- Email: [email protected]
Lithium suppresses ovariectomy-induced surges in plasma gonadotropins in rats
Life Sciences, Vol. 44, pp. 1363-1369 Printed in the U.S.A.
LITHIUM
SUPPRESSES 0VARIECTOMY-INDUCED IN PLASMA GONADOTROPIN8 IN RATS
Pergamon Press
SURGES
S.H. Sheikha,* L.S. LeGate,** and T.K. Banerji* Department of Anatomy and Neurosciences* and Department of Pathology** The University of Texas Medical Branch, Galveston, Texas 77550 (Received in final form Hatch 3, 1989)
Summary We have reported earlier that administration of lithium, the widely-used drug for the treatment of acute mania and prophylaxis of recurrent manic-depressive bipolar disorders, leads to a disruption of estrous cycle and a significant suppression of the proestrous surge of luteinizing hormone (LH) in a number of laboratory rodents. In this report we have examined the effects of this antimanic drug on plasma and pituitary levels of LH and follicle stimulating hormone (FSH) in rats following ovariectomy (OVX), an altered endocrine state in which the levels of serum LH and FSH are highly and chronically elevated. Adult OVX rats, maintained under standardized laboratory conditions (LD 12: 12; white lights on at 06.00 h, CST) were injected (ip) with lithium, 40 days post-operation, at a dosage of 3.0 and 2.0 mEq/Kg b. wt. for 3 and 7 days respectively (twice daily at 08.00 and 16.00 h). Control OVX rats received nothing or saline injections, whereas an intact control (C) received no surgical manipulation or drug injections of any kind. As expected, the levels of plasma LH and FSH in OVX (only) group showed nearly 6-fold and 75-fold increase respectively compared to those in C. Lithium injections in OVX rats for 3 and 7 days resulted in a significant reduction in plasma LH (P<.005 and P<.02 respectively) and FSH (P<.O01) levels when compared with those in the OVX control groups. Lithium also led to a significant reduction in the levels of pituitary LH after both 3 (P<.02) and 7 days (P<.02), but the levels of pituitary FSH remained unchanged. These results suggest that the pituitary gonadotropes constitute a definitive target for lithium's action, either directly or via the hypothalamus. The recognition of lithium as a substance of psychopharmacological importance can be traced back to 1949, the year when Cade (i) showed that this alkali metal has clinical usefulness in affective disorders. The therapeutic utility of lithium has since been firmly established, and lithium currently remains the drug of choice for acute mania (2-5) as well as for prophylactic maintenance of patients with recurrent bipolar affective disorders (6-8). Although the available evidence clearly indicates the therapeutic effects of lithium salts in manic-depressive episodes, the mechanisms of action by which lithium brings this about remain largely obscure. Reprint request to Dr. T.K. Banerji
0024-3205/89 $3.00 + .00 Copyright (c) 1989 Pergamon Press plc
1364
Effects of Lithium on LH and FSH in OVX Rats
Vol. 44, No, 19, 1989
From the published data over the past few years, it has become increasingly apparent that prolonged treatment with this antipsychotic drug may be associated with a plethora of metabolic and endocrine effects (9,10). Recent reports from a number of laboratories have also indicated that lithium may have significant adverse effects on the male reproductive system of both human (11-12) and experimental laboratory animals (13-17). There is a relative tendency for w o m e n to develop m a n i c - d e p r e s s i v e psychosis more often than men and the age of maximum risk coincides with the potential procreative years of the woman (18,19). It is unfortunate, however, that very little is k n o w n about lithium's reproductive effects in the h u m a n female. Utilizing laboratory animals, we have recently reported that lithium indeed has significant adverse effects on the female reproductive system. Thus, acute a d m i n i s t r a t i o n of lithium leads to a significant suppression of the proestrous surge of luteinizing hormone (LH) in mice and hamsters, whereas chronic treatment with this ion results in the loss of normal estrous cyclicity in mice (20,21). Though these results, important from both basic and clinical standpoints, suggested that lithium affects the hypothalamicpituitary-ovarian axis, it is not known whether this was mediated centrally or peripherally at the level of the gonad. In this paper we have attempted to address this issue by examining the effects of lithium on the levels of plasma and pituitary gonadotropins following long-term ovariectomy - an experimentally altered endocrine state in which due to the absence of the negative feedback control from the ovary, there is a chronic and high magnitude elevation in the levels of plasma LH and FSH.
Materials
and M e t h o d s
Adult female Sprague-Dawley rats (weighing 200-250 g) were obtained from Timco Breeding Company, Houston, TX, and were housed in a temperature- and light-controlled room, with lights on from 06:00 to 18:00 h (CST). Food and water were provided ad libitum. Animals were allowed to acclimatize for 2 weeks prior to use in any experiment. Groups of rats were bilaterally o v a r i e c t o m i z e d (OVX) under ether anesthesia. A skin incision running lengthwise about 2 cm lateral to the dorsal mid-line, and running approximately from in front of the hip to a point somewhat anterior to the upper pole of the kidney. The uterine horns and ovaries were located, the uterus was ligated just below the fallopian tube, tied tightly, and the ovaries were removed. The muscle incision was closed by silk thread sutures, and the skin incision with wound clips. Rats were then returned to their cages. Following 40 days of ovariectomy, lithium injections were started. Lithium chloride (Sigma Chemical Company, St. Louis, MO) was dissolved in sterile distilled water, and injected intraperitoneally into the OVX rats twice daily at 08:00 and 16:00 h at a dosage of 3.0 and 2.0 mEQ/Kg body weight for 3 and 7 days, respectively. Control OVX rats received saline injections at the same hour and in equal volumes. In addition, a group of OVX only was also included. The animals of this group did not receive lithium or saline injections. Another intact control, undergoing no surgical procedures, nor receiving injections of any test substances, was also included in order to evaluate the magnitude of increase in gonadotropins following OVX. OVX rats receiving either lithium or saline injections were sacrificed at 12:00 h, which is 4 hours after the last morning injection. OVX rats receiving no other treatment were also sacrificed at the same hour. The group of intact control rats was sacrificed at the same hour on the day of metestrus. Blood was collected in heparinized tubes kept in ice. The brain was dissected
Vol. 44, No. 19, 1989
Effects of Lithium on LH and FSH in OVX Rats
1365
and the pituitary gland was immediately removed, weighed and homogenized in i ml of 0.01 M phosphate buffered saline (PBS) containing 0.05 M EDTA and 0.1% sodium azide (pH 7.6). The blood and pituitary homogenates were centrifuged at i000 X g for 15 minutes at 4°C and the plasma and supernatant of pituitary homogenates were stored frozen at -70°C until used for the measurement of LH and FSH by RIA. The concentration of lithium in plasma was measured by a flame photometer. Plasma and pituitary LH and FSH were measured by RIA using the NIADDK RIA kit according to procedures described by Beamer et al (22). Duplicate i00 ~I samples of plasma were measured for LH and FSH levels, while pituitary LH and FSH were measured in duplicate of I00 #i aliquots of i:i000 dilution of the supernatant from pituitary homogenates for LH and i:i0 dilution for FSH. The hormonal content of the samples was expressed as ng of either NIADDK-rLH-RP-2 and as #g of NIADDK-rFSH-RP-2, per ml plasma (or ng/~g pituitary wet weight). Intra-assay coefficient of variation was less than 9% for both LH and FSH, and the inter-assay coefficient of variations for LH and FSH were 12% and 7%, respectively.
Results Following bilateral ovariectomy, plasma LH was significantly increased (P<.005) as expected. Ovariectomy also led to a significant (P<.001) increase in plasma FSH (Fig. i). Pituitary levels of FSH and LH were also significantly increased (P<.001) in OVX rats compared to those of intact rats in metestrus (Fig. 2). Lithium administration in OVX rats for 3 days led to a significant reduction in the levels of plasma LH (P<.005) and FSH (P<.O01) (Fig. I). When lithium injections were continued for 7 days, the levels of plasma LH and FSH remained significantly (P<.02 and P<.O01, respectively) suppressed (Fig. i), as compared to those of the matched OVX controls receiving saline injections. Pituitary levels of LH in OVX rats showed a significant reduction (P<.02) following both 3 and 7 days of lithium administration as compared to OVX control rats injected with saline (Fig. 2). However, no significant changes were evident in the levels of pituitary FSH following either 3 or 7 days of lithium treatment (Fig. 2). The concentrations of plasma lithium, expressed in mEQ/I, were: 1.5 ± 0.01 (mean ± S.E.M.) and 1.4 ± 0.05 following 3 and 7 days of lithium treatment, respectively.
Discussion Earlier studies from our laboratory have suggested that lithium administration in intact female rodents leads to significant alterations in the circulating levels of LH (20,21). In the present study, 40 days following ovariectomy, pituitary gonadotropes responded in the expected manner as evidenced by highly elevated levels of plasma LH and FSH. Apparently following surgical removal of the ovaries, the negative feedback is lost and the system becomes essentially an open-loop, resulting in the production and release of large quantities of LH and FSH. The purpose of this experiment was to chronically increase the levels of gonadotropins by creating this open loop and eliminating the influence of the ovarian steroids, and then to examine whether lithium can still modulate the levels of gonadotropins under this altered state of the hypothalamo-pituitary gonadal axis.
1366
Effects
of L i t h i u m
on LH and FSH in OVX Rats
Vol.
44, No.
19, 1989
It is i n t e r e s t i n g to note that l i t h i u m i n j e c t i o n s for 3 a n d 7 days in ovariectomized rats, a c o n d i t i o n w h e r e the p l a s m a g o n a d o t r o p i n l e v e l s increased dramatically (LH: 6-fold; FSH: 75-fold), led to a s i g n i f i c a n t supp r e s s i o n of these very h i g h levels of the two hormones. These results indicate that even w h e n the aberrant endocrine m i l i e u r e s u l t i n g from removal of the ovarian compartment is present, lithium can exert its insult on the
Intact control
I
OVX only OVX + Saline OVX + Lithium
~/// p
Z
p
-
I
~
I
, ....,
mE E ~ ~m i
-
c
v
3 Days7 Days 20301. . . . . .
--
Pi0"0011
0
3 Days7 Days FIG.
1
E f f e c t s of l i t h i u m a d m i n i s t r a t i o n in O V X rats on the l e v e l s of p l a s m a LH a n d FSH. The v a l u e s are m e a n ± S.E.M. S t a t i s t i c a l sign i f i c a n c e is tested according to 2-tailed student's t test.
p i t u i t a r y gonadotropes. Conceptual evidence to this idea is also p r o v i d e d by our recent report (23) showing that the chronic and high m a g n i t u d e e l e v a t i o n of circulating gonadotropins which results from c a s t r a t i o n in male rats is significantly suppressed following lithium a d m i n i s t r a t i o n for 5 days. Taken together, these r e s u l t s s u g g e s t that the a n t i m a n i c e f f e c t s of l i t h i u m are m e d i a t e d centrally, although a p e r i p h e r a l effect can not be ruled out. W h e t h e r
Vol. 44, No. 19, 1989
Effects of Lithium on LH and FSH in OVX Rats
1367
the suppression of gonadotropins in OVX rats following lithium was mediated by the hypothalamus or whether this was directed at the pituitary, remain unknown, however. In post-menopausal women the plasma concentrations of both LH and FSH rise significantly and remain elevated. These hormonal changes are usually accompanied by a variety of other functional changes, such as vasomotor instability and wide fluctuations of blood pressure. Most women in menopause
[--)
Intaot oontrol OVX only OVX + Saline ITTT~ OVX + Lithium
3~,.. 80t ~,0) 60'- :::l
"5 m 40~v
Q.
2O0
Z
3 Days7 Days
401 p
I " '[11
3 Days7 Days FIG. 2
Changes in the levels of pituitary I/4 and FSH in OVX rats following injections of lithium. The values are mean ± S.E.M. 2-tailed student's t test was used for statistical significance.
experience "hot flushes" during which there is a marked vasodilation of the peripheral vessels supplying the face and upper parts of the body. Although the interrelations between hot flushes and elevated levels of LH and FSH in post-menopausal women has not been clearly elucidated, some authors have suggested that there is a causal relationship between these (24). The significant reduction by lithium of plasma LH and FSH in the OVX rats, noted
1368
Effects of Lithium on LH and FSH in OVX Rats
Vol. 44, No. 19, 1989
in this experiment are noteworthy therefore since the OVX rats clearly simulate the condition attained in menopause, especially in regard to the significantly elevated levels of gonadotropins. Thus, it remains u n k n o w n whether lithium has any ameliorating effect on hot flushes in post-menopausal women who are on chronic prophylactic therapy. In addition to the levels of plasma LH, pituitary LH c o n c e n t r a t i o n was also affected by lithium treatment after both 3 and 7 days in the OVX rats. Results from previous studies in castrated male rats (23) indicated that lithium affects only the circulating levels of LH, rather than the levels of this hormone w i t h i n the pituitary. However, in the present experiment, lithium apparently affected the process of both secretion and synthesis of gonadotropins, since the pituitary as well as plasma LH levels were altered following lithium treatment. The apparent reduction in the circulating levels of gonadotropins following lithium could also be due to an altered rate of clearance of these hormones. Compared to most other psyochopharmacological drugs, lithium has a rather narrow therapeutic index. Although most clinicians recommend a serum lithium c o n c e n t r a t i o n of 0.8 to 1.2 mmol/l for prophylaxis of recurrent affective disorders, other investigators believe that a range of 0.5 to 1.5 mmol/l should be considered therapeutic (25,26). In view of this, it should be noted that the significant reduction in plasma and pituitary gonadotropins was evident when the mean plasma lithium concentrations of the ion were 1.5 and 1.4 mmol/l (3 and 7 days of treatment, respectively) levels w h i c h were attained only 4, rather than 12, hours after the last lithium injection. The gonadotropin suppressing effects noted in the present experiment, therefore, were manifested under a therapeutic lithium concentration, and thus, may have clinical implications. In conclusion, our results suggest that the pituitary gland is a target for lithium's action and that lithium exerts a suppressive effect on the secretion of pituitary LH and FSH. More experimental data will be required in order to identify whether these effects were mediated by the hypothalamus.
Acknowledeqments This work was supported in part by a scholarship from the Jordan U n i v e r s i t y of Science and Technology, Irbid, Jordan, to S.H.S. We are thankful to Dr. T.J. Collins for providing some of the laboratory facilities for RIA and the rat Pituitary Hormone Distribution Program of the NIADDK for supplying the materials used in RIA of LH and FSH. We also thank Amir Rassoli for expert technical assistance.
References i. 2. 3.
4. 5. 6. 7. 8.
J.F.J. CADE, Med. J. Aust. 2 349-352 (1949). S. GERSHON, Clin. Pharmacol. Ther. II 168-187 (1970). F.K. GOODWIN, D.L. MURPHY and W.E. BUNNY, Arch. Gen. Psychiat. 21 486-496 (1969). J . H . KOCSIS, I n Handbook o f L i t h i u m T h e r a p y , F.N. J o h n s o n e d , pp. 9 - 1 5 , University Park Press, Baltimore (1980). P.F. PRIEN, Clin. Neuropharmacol. ~ 113-131 (1978). J.W. JEFFERSON and J.H. GREIST, Primer of Lithium Therapy, Williams and Wilkins, Baltimore (1977). M. SCHOU, J. Psychiat. Res. 6 67-95 (1968). M. SCHOU, and L. THOMSEN, In Lithium Prophylaxis of Recurrent Endogenous Affective Disorders F.N. Johnson ed, pp. 63-83, Academic Press, New York (1975).
Vol. 44, No. 19, 1989
9. i0. ii. 12. 13.
14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26.
Effects of Lithium on LH and FSH in OVX Rats
1369
J.H. LAZARUS, Endocrine and Metabolic Effects of Lithium, Plenum Publishing Corporation (1986). P.T. MANNISTO, In Handbook of Lithium Therapy, F.N. Johnson ed, pp. 310-322, University Park Press, Baltimore (1980). R.S. SANCHEZ, G.G. MURTHY, J. MEHTA, W.W. SHREEVE and F.R. SINGH, Fert. Steril. 27 667-669 (1976). M.H. SHEARD, J.L. MARINI, and S.S. GIDDINGS, Dis. Nerv. Syst. 38 765-769 (1977). T.K. BANERJI, In Lithium and Endocrine System, Lithium Therapy Monographs, F.N. Johnson ed, vol. 2 pp. 51-62, S. Karger, Basel, Switzerland (1988). T.K. BANERJI, T.A. PARKENING, and T.J. COLLINS, Life Sci. 3__O0 1045-1050 (1982). T.K. BANERJI, T.A. PARKENING, T.J. COLLINS and A. RASSOLI, Life Sci. 3_/3 1621-1627 (1983). V. PRASAD and M.H. SHEARD, Comm. Psychopharmacolo 4 147-152 (1980). S.H. SHEIKHA, T.J. COLLINS, A.H. RASSOLI, L.S. LEGATE and T.K. BANERJI, Life Sci. 40 1835-1844 (1987). J.-M. LEMOINE, In Depression and Mania: Modern Lithium Therapy, F.N. Johnson ed, pp. 139-146, IRL Press, Oxford (1987). J. SPIEGEL and N. BELL, In American Handbook of Psychiatry, S. Arieti ed, pp. 114-149, Basic Books, New York (1959). T.K. BANERJI, T.A. PARKENING, T.J. COLLINS, A.H. RASSOLI and L.S. LEGATE, Brain Res. 380 176-180 (1986). T.K. BANERJI, T.J. COLLINS, T.A. PARKENING, A.H. RASSOLI, S.H. SHEIKHA and L.S. LEGATE, IRCS Med. Sci. 14 523-524 (1986). W.G. BEAMER, S.M. MURR and I.J. GESCHEWIND, Endocrinology 90 823-827 (1972). S.H. SHEIKHA, T.J. COLLINS, A.H. RASSOLI, L.S. LEGATE and T.K. BANERJI, IRCS Med. Sci. 14 912-913 (1986). C.R. Martin, Endocrine Physiology, pp. 620-680, Oxford University Press, New York (1985). D.F. KLEIN and J.M. DAVIS, Diagnosis and Treatment of Psychiatric Disorders, Williams and Wilkins, Baltimore, Maryland (1969). R.F. PRIEN, E.M. CAFFEY JR. and C.J. KLETT, Br. J. Psychiat. 120 409-414 (1970).
LITHIUM
SUPPRESSES 0VARIECTOMY-INDUCED IN PLASMA GONADOTROPIN8 IN RATS
Pergamon Press
SURGES
S.H. Sheikha,* L.S. LeGate,** and T.K. Banerji* Department of Anatomy and Neurosciences* and Department of Pathology** The University of Texas Medical Branch, Galveston, Texas 77550 (Received in final form Hatch 3, 1989)
Summary We have reported earlier that administration of lithium, the widely-used drug for the treatment of acute mania and prophylaxis of recurrent manic-depressive bipolar disorders, leads to a disruption of estrous cycle and a significant suppression of the proestrous surge of luteinizing hormone (LH) in a number of laboratory rodents. In this report we have examined the effects of this antimanic drug on plasma and pituitary levels of LH and follicle stimulating hormone (FSH) in rats following ovariectomy (OVX), an altered endocrine state in which the levels of serum LH and FSH are highly and chronically elevated. Adult OVX rats, maintained under standardized laboratory conditions (LD 12: 12; white lights on at 06.00 h, CST) were injected (ip) with lithium, 40 days post-operation, at a dosage of 3.0 and 2.0 mEq/Kg b. wt. for 3 and 7 days respectively (twice daily at 08.00 and 16.00 h). Control OVX rats received nothing or saline injections, whereas an intact control (C) received no surgical manipulation or drug injections of any kind. As expected, the levels of plasma LH and FSH in OVX (only) group showed nearly 6-fold and 75-fold increase respectively compared to those in C. Lithium injections in OVX rats for 3 and 7 days resulted in a significant reduction in plasma LH (P<.005 and P<.02 respectively) and FSH (P<.O01) levels when compared with those in the OVX control groups. Lithium also led to a significant reduction in the levels of pituitary LH after both 3 (P<.02) and 7 days (P<.02), but the levels of pituitary FSH remained unchanged. These results suggest that the pituitary gonadotropes constitute a definitive target for lithium's action, either directly or via the hypothalamus. The recognition of lithium as a substance of psychopharmacological importance can be traced back to 1949, the year when Cade (i) showed that this alkali metal has clinical usefulness in affective disorders. The therapeutic utility of lithium has since been firmly established, and lithium currently remains the drug of choice for acute mania (2-5) as well as for prophylactic maintenance of patients with recurrent bipolar affective disorders (6-8). Although the available evidence clearly indicates the therapeutic effects of lithium salts in manic-depressive episodes, the mechanisms of action by which lithium brings this about remain largely obscure. Reprint request to Dr. T.K. Banerji
0024-3205/89 $3.00 + .00 Copyright (c) 1989 Pergamon Press plc
1364
Effects of Lithium on LH and FSH in OVX Rats
Vol. 44, No, 19, 1989
From the published data over the past few years, it has become increasingly apparent that prolonged treatment with this antipsychotic drug may be associated with a plethora of metabolic and endocrine effects (9,10). Recent reports from a number of laboratories have also indicated that lithium may have significant adverse effects on the male reproductive system of both human (11-12) and experimental laboratory animals (13-17). There is a relative tendency for w o m e n to develop m a n i c - d e p r e s s i v e psychosis more often than men and the age of maximum risk coincides with the potential procreative years of the woman (18,19). It is unfortunate, however, that very little is k n o w n about lithium's reproductive effects in the h u m a n female. Utilizing laboratory animals, we have recently reported that lithium indeed has significant adverse effects on the female reproductive system. Thus, acute a d m i n i s t r a t i o n of lithium leads to a significant suppression of the proestrous surge of luteinizing hormone (LH) in mice and hamsters, whereas chronic treatment with this ion results in the loss of normal estrous cyclicity in mice (20,21). Though these results, important from both basic and clinical standpoints, suggested that lithium affects the hypothalamicpituitary-ovarian axis, it is not known whether this was mediated centrally or peripherally at the level of the gonad. In this paper we have attempted to address this issue by examining the effects of lithium on the levels of plasma and pituitary gonadotropins following long-term ovariectomy - an experimentally altered endocrine state in which due to the absence of the negative feedback control from the ovary, there is a chronic and high magnitude elevation in the levels of plasma LH and FSH.
Materials
and M e t h o d s
Adult female Sprague-Dawley rats (weighing 200-250 g) were obtained from Timco Breeding Company, Houston, TX, and were housed in a temperature- and light-controlled room, with lights on from 06:00 to 18:00 h (CST). Food and water were provided ad libitum. Animals were allowed to acclimatize for 2 weeks prior to use in any experiment. Groups of rats were bilaterally o v a r i e c t o m i z e d (OVX) under ether anesthesia. A skin incision running lengthwise about 2 cm lateral to the dorsal mid-line, and running approximately from in front of the hip to a point somewhat anterior to the upper pole of the kidney. The uterine horns and ovaries were located, the uterus was ligated just below the fallopian tube, tied tightly, and the ovaries were removed. The muscle incision was closed by silk thread sutures, and the skin incision with wound clips. Rats were then returned to their cages. Following 40 days of ovariectomy, lithium injections were started. Lithium chloride (Sigma Chemical Company, St. Louis, MO) was dissolved in sterile distilled water, and injected intraperitoneally into the OVX rats twice daily at 08:00 and 16:00 h at a dosage of 3.0 and 2.0 mEQ/Kg body weight for 3 and 7 days, respectively. Control OVX rats received saline injections at the same hour and in equal volumes. In addition, a group of OVX only was also included. The animals of this group did not receive lithium or saline injections. Another intact control, undergoing no surgical procedures, nor receiving injections of any test substances, was also included in order to evaluate the magnitude of increase in gonadotropins following OVX. OVX rats receiving either lithium or saline injections were sacrificed at 12:00 h, which is 4 hours after the last morning injection. OVX rats receiving no other treatment were also sacrificed at the same hour. The group of intact control rats was sacrificed at the same hour on the day of metestrus. Blood was collected in heparinized tubes kept in ice. The brain was dissected
Vol. 44, No. 19, 1989
Effects of Lithium on LH and FSH in OVX Rats
1365
and the pituitary gland was immediately removed, weighed and homogenized in i ml of 0.01 M phosphate buffered saline (PBS) containing 0.05 M EDTA and 0.1% sodium azide (pH 7.6). The blood and pituitary homogenates were centrifuged at i000 X g for 15 minutes at 4°C and the plasma and supernatant of pituitary homogenates were stored frozen at -70°C until used for the measurement of LH and FSH by RIA. The concentration of lithium in plasma was measured by a flame photometer. Plasma and pituitary LH and FSH were measured by RIA using the NIADDK RIA kit according to procedures described by Beamer et al (22). Duplicate i00 ~I samples of plasma were measured for LH and FSH levels, while pituitary LH and FSH were measured in duplicate of I00 #i aliquots of i:i000 dilution of the supernatant from pituitary homogenates for LH and i:i0 dilution for FSH. The hormonal content of the samples was expressed as ng of either NIADDK-rLH-RP-2 and as #g of NIADDK-rFSH-RP-2, per ml plasma (or ng/~g pituitary wet weight). Intra-assay coefficient of variation was less than 9% for both LH and FSH, and the inter-assay coefficient of variations for LH and FSH were 12% and 7%, respectively.
Results Following bilateral ovariectomy, plasma LH was significantly increased (P<.005) as expected. Ovariectomy also led to a significant (P<.001) increase in plasma FSH (Fig. i). Pituitary levels of FSH and LH were also significantly increased (P<.001) in OVX rats compared to those of intact rats in metestrus (Fig. 2). Lithium administration in OVX rats for 3 days led to a significant reduction in the levels of plasma LH (P<.005) and FSH (P<.O01) (Fig. I). When lithium injections were continued for 7 days, the levels of plasma LH and FSH remained significantly (P<.02 and P<.O01, respectively) suppressed (Fig. i), as compared to those of the matched OVX controls receiving saline injections. Pituitary levels of LH in OVX rats showed a significant reduction (P<.02) following both 3 and 7 days of lithium administration as compared to OVX control rats injected with saline (Fig. 2). However, no significant changes were evident in the levels of pituitary FSH following either 3 or 7 days of lithium treatment (Fig. 2). The concentrations of plasma lithium, expressed in mEQ/I, were: 1.5 ± 0.01 (mean ± S.E.M.) and 1.4 ± 0.05 following 3 and 7 days of lithium treatment, respectively.
Discussion Earlier studies from our laboratory have suggested that lithium administration in intact female rodents leads to significant alterations in the circulating levels of LH (20,21). In the present study, 40 days following ovariectomy, pituitary gonadotropes responded in the expected manner as evidenced by highly elevated levels of plasma LH and FSH. Apparently following surgical removal of the ovaries, the negative feedback is lost and the system becomes essentially an open-loop, resulting in the production and release of large quantities of LH and FSH. The purpose of this experiment was to chronically increase the levels of gonadotropins by creating this open loop and eliminating the influence of the ovarian steroids, and then to examine whether lithium can still modulate the levels of gonadotropins under this altered state of the hypothalamo-pituitary gonadal axis.
1366
Effects
of L i t h i u m
on LH and FSH in OVX Rats
Vol.
44, No.
19, 1989
It is i n t e r e s t i n g to note that l i t h i u m i n j e c t i o n s for 3 a n d 7 days in ovariectomized rats, a c o n d i t i o n w h e r e the p l a s m a g o n a d o t r o p i n l e v e l s increased dramatically (LH: 6-fold; FSH: 75-fold), led to a s i g n i f i c a n t supp r e s s i o n of these very h i g h levels of the two hormones. These results indicate that even w h e n the aberrant endocrine m i l i e u r e s u l t i n g from removal of the ovarian compartment is present, lithium can exert its insult on the
Intact control
I
OVX only OVX + Saline OVX + Lithium
~/// p
Z
p
-
I
~
I
, ....,
mE E ~ ~m i
-
c
v
3 Days7 Days 20301. . . . . .
--
Pi0"0011
0
3 Days7 Days FIG.
1
E f f e c t s of l i t h i u m a d m i n i s t r a t i o n in O V X rats on the l e v e l s of p l a s m a LH a n d FSH. The v a l u e s are m e a n ± S.E.M. S t a t i s t i c a l sign i f i c a n c e is tested according to 2-tailed student's t test.
p i t u i t a r y gonadotropes. Conceptual evidence to this idea is also p r o v i d e d by our recent report (23) showing that the chronic and high m a g n i t u d e e l e v a t i o n of circulating gonadotropins which results from c a s t r a t i o n in male rats is significantly suppressed following lithium a d m i n i s t r a t i o n for 5 days. Taken together, these r e s u l t s s u g g e s t that the a n t i m a n i c e f f e c t s of l i t h i u m are m e d i a t e d centrally, although a p e r i p h e r a l effect can not be ruled out. W h e t h e r
Vol. 44, No. 19, 1989
Effects of Lithium on LH and FSH in OVX Rats
1367
the suppression of gonadotropins in OVX rats following lithium was mediated by the hypothalamus or whether this was directed at the pituitary, remain unknown, however. In post-menopausal women the plasma concentrations of both LH and FSH rise significantly and remain elevated. These hormonal changes are usually accompanied by a variety of other functional changes, such as vasomotor instability and wide fluctuations of blood pressure. Most women in menopause
[--)
Intaot oontrol OVX only OVX + Saline ITTT~ OVX + Lithium
3~,.. 80t ~,0) 60'- :::l
"5 m 40~v
Q.
2O0
Z
3 Days7 Days
401 p
I " '[11
3 Days7 Days FIG. 2
Changes in the levels of pituitary I/4 and FSH in OVX rats following injections of lithium. The values are mean ± S.E.M. 2-tailed student's t test was used for statistical significance.
experience "hot flushes" during which there is a marked vasodilation of the peripheral vessels supplying the face and upper parts of the body. Although the interrelations between hot flushes and elevated levels of LH and FSH in post-menopausal women has not been clearly elucidated, some authors have suggested that there is a causal relationship between these (24). The significant reduction by lithium of plasma LH and FSH in the OVX rats, noted
1368
Effects of Lithium on LH and FSH in OVX Rats
Vol. 44, No. 19, 1989
in this experiment are noteworthy therefore since the OVX rats clearly simulate the condition attained in menopause, especially in regard to the significantly elevated levels of gonadotropins. Thus, it remains u n k n o w n whether lithium has any ameliorating effect on hot flushes in post-menopausal women who are on chronic prophylactic therapy. In addition to the levels of plasma LH, pituitary LH c o n c e n t r a t i o n was also affected by lithium treatment after both 3 and 7 days in the OVX rats. Results from previous studies in castrated male rats (23) indicated that lithium affects only the circulating levels of LH, rather than the levels of this hormone w i t h i n the pituitary. However, in the present experiment, lithium apparently affected the process of both secretion and synthesis of gonadotropins, since the pituitary as well as plasma LH levels were altered following lithium treatment. The apparent reduction in the circulating levels of gonadotropins following lithium could also be due to an altered rate of clearance of these hormones. Compared to most other psyochopharmacological drugs, lithium has a rather narrow therapeutic index. Although most clinicians recommend a serum lithium c o n c e n t r a t i o n of 0.8 to 1.2 mmol/l for prophylaxis of recurrent affective disorders, other investigators believe that a range of 0.5 to 1.5 mmol/l should be considered therapeutic (25,26). In view of this, it should be noted that the significant reduction in plasma and pituitary gonadotropins was evident when the mean plasma lithium concentrations of the ion were 1.5 and 1.4 mmol/l (3 and 7 days of treatment, respectively) levels w h i c h were attained only 4, rather than 12, hours after the last lithium injection. The gonadotropin suppressing effects noted in the present experiment, therefore, were manifested under a therapeutic lithium concentration, and thus, may have clinical implications. In conclusion, our results suggest that the pituitary gland is a target for lithium's action and that lithium exerts a suppressive effect on the secretion of pituitary LH and FSH. More experimental data will be required in order to identify whether these effects were mediated by the hypothalamus.
Acknowledeqments This work was supported in part by a scholarship from the Jordan U n i v e r s i t y of Science and Technology, Irbid, Jordan, to S.H.S. We are thankful to Dr. T.J. Collins for providing some of the laboratory facilities for RIA and the rat Pituitary Hormone Distribution Program of the NIADDK for supplying the materials used in RIA of LH and FSH. We also thank Amir Rassoli for expert technical assistance.
References i. 2. 3.
4. 5. 6. 7. 8.
J.F.J. CADE, Med. J. Aust. 2 349-352 (1949). S. GERSHON, Clin. Pharmacol. Ther. II 168-187 (1970). F.K. GOODWIN, D.L. MURPHY and W.E. BUNNY, Arch. Gen. Psychiat. 21 486-496 (1969). J . H . KOCSIS, I n Handbook o f L i t h i u m T h e r a p y , F.N. J o h n s o n e d , pp. 9 - 1 5 , University Park Press, Baltimore (1980). P.F. PRIEN, Clin. Neuropharmacol. ~ 113-131 (1978). J.W. JEFFERSON and J.H. GREIST, Primer of Lithium Therapy, Williams and Wilkins, Baltimore (1977). M. SCHOU, J. Psychiat. Res. 6 67-95 (1968). M. SCHOU, and L. THOMSEN, In Lithium Prophylaxis of Recurrent Endogenous Affective Disorders F.N. Johnson ed, pp. 63-83, Academic Press, New York (1975).
Vol. 44, No. 19, 1989
9. i0. ii. 12. 13.
14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26.
Effects of Lithium on LH and FSH in OVX Rats
1369
J.H. LAZARUS, Endocrine and Metabolic Effects of Lithium, Plenum Publishing Corporation (1986). P.T. MANNISTO, In Handbook of Lithium Therapy, F.N. Johnson ed, pp. 310-322, University Park Press, Baltimore (1980). R.S. SANCHEZ, G.G. MURTHY, J. MEHTA, W.W. SHREEVE and F.R. SINGH, Fert. Steril. 27 667-669 (1976). M.H. SHEARD, J.L. MARINI, and S.S. GIDDINGS, Dis. Nerv. Syst. 38 765-769 (1977). T.K. BANERJI, In Lithium and Endocrine System, Lithium Therapy Monographs, F.N. Johnson ed, vol. 2 pp. 51-62, S. Karger, Basel, Switzerland (1988). T.K. BANERJI, T.A. PARKENING, and T.J. COLLINS, Life Sci. 3__O0 1045-1050 (1982). T.K. BANERJI, T.A. PARKENING, T.J. COLLINS and A. RASSOLI, Life Sci. 3_/3 1621-1627 (1983). V. PRASAD and M.H. SHEARD, Comm. Psychopharmacolo 4 147-152 (1980). S.H. SHEIKHA, T.J. COLLINS, A.H. RASSOLI, L.S. LEGATE and T.K. BANERJI, Life Sci. 40 1835-1844 (1987). J.-M. LEMOINE, In Depression and Mania: Modern Lithium Therapy, F.N. Johnson ed, pp. 139-146, IRL Press, Oxford (1987). J. SPIEGEL and N. BELL, In American Handbook of Psychiatry, S. Arieti ed, pp. 114-149, Basic Books, New York (1959). T.K. BANERJI, T.A. PARKENING, T.J. COLLINS, A.H. RASSOLI and L.S. LEGATE, Brain Res. 380 176-180 (1986). T.K. BANERJI, T.J. COLLINS, T.A. PARKENING, A.H. RASSOLI, S.H. SHEIKHA and L.S. LEGATE, IRCS Med. Sci. 14 523-524 (1986). W.G. BEAMER, S.M. MURR and I.J. GESCHEWIND, Endocrinology 90 823-827 (1972). S.H. SHEIKHA, T.J. COLLINS, A.H. RASSOLI, L.S. LEGATE and T.K. BANERJI, IRCS Med. Sci. 14 912-913 (1986). C.R. Martin, Endocrine Physiology, pp. 620-680, Oxford University Press, New York (1985). D.F. KLEIN and J.M. DAVIS, Diagnosis and Treatment of Psychiatric Disorders, Williams and Wilkins, Baltimore, Maryland (1969). R.F. PRIEN, E.M. CAFFEY JR. and C.J. KLETT, Br. J. Psychiat. 120 409-414 (1970).