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Action of prolactin on the uropygial gland of chicks
GENERAL
AND
COMPARATIVE
Action
38,461-465
ENDGCRINOLOGY
of Prolactin
on the Uropygial B.R.
SUBRATA~HAKRABORTY,* *Histophysiology Road, Calcutta
Laboratory, 7000/9. and
(1979)
Department tEndocrinology
MAITI,*
of Zoology, Laboratory, West Bengal,
Gland
AND S.P.
University Department India
of Chicks
BHATTACHARYYA?
of Calcutta, 35 Ballygunge of Zoology, University
Circular of Kalyani,
Accepted May 1, 1979 The aim of the present investigation was to ascertain the role of prolactin on the uropygial gland of chicks. The investigation was carried out by histological, karyodynamic, and biochemical studies. Ovine prolactin treatment in both low and high dosages increased the mitotic incidence but suppressed the wax content of the uropygial gland. It appears that although- prolactin can promote mitosis in the uropygial gland of chicks, it does not appear to _ stimulate the glandular function. gland (Maiti, 1968). The birds were killed by cervical dislocation 24 hr after the last injection of the hormone. The uropygial glands were dissected out, placed in Bouin’s fixative, and processed for histological and karyodynamic studies. Histological investigation was performed from the uropygial gland sections (5 pm) after staining with Masson’s technique. The karyodynamic investigation was carried out by staining the gland sections with iron-alum-hemotoxylin. Two thousand differential cells (viz., metaphase, healthy, and pycnotic) were counted at random from each gland for each bird and respective percentages of these cells were calculated. Total lipid content of the uropygial gland was estimated following the method of Folch et al. (1957). Free fatty acids were separated from total lipids following extraction with 0.5 N sodium hydroxide (Mackenna et al., 1950). Mono- and diester waxes of the glandular lipids were separated by column chromatography on silicic acid using cyclohexane and benzene as the solvent gradients (Jacob, 1975). Following saponification, corresponding wax alcohols were also analysed by thin layer chromatography on silica gel G-coated plates (Game, 1971) (Fig. 4). Benzene-ethyl acetate (9 : I v/v) was used as the solvent system for this purpose.
There are some indications that prolactin both directly stimulates the sebaceous glands and increases their response to testosterone and progesterone in intact or hypophysectomized rats (Callahan, 1959; Ebling e? al., 1969, 1975). But this has been disputed by others (Lorincz, 1963; Nikkari and Valavaara, 1970; Shuster and Thody, 1974) who did not find such action of prolactin in these rats. The avian uropygial gland resembles the sebaceous glands in structure, function, and hormonal regulation (Maiti and Ghosh, 1972; Maiti el al., 1979; cf. Ebling, 1963). But as yet the role of prolactin on the uropygial gland is not known. Thus it was investigated in the current paper. MATERIALS
AND METHODS
Fifteen-day-old male chicks (Leghorn) (body weight: between 70-80 g) were procured from a local poultry farm and maintained in uniform husbandry conditions in the laboratory with standard poultry feed and water ad libitum. Sixty birds were divided equally into three groups (viz., A, B, and C). The first group was kept for control and the remaining groups for hormone treatment. Purified ovine prolactin (NIH-LTH, USA) was dissolved in normal saline and injected intramuscularly in two dosages (see Table 1). Some of the birds belonging to both control and treated groups were injected intraperitoneally with colchicine (0.1 mg/lOO g body wt) at 6 hr prior to autopsy, for mitotic studies. The colchicine treatment was administered at the optimum time (10 PM to 4 AM) for obtaining maximum mitotic cells in the uropygial
RESULTS Gross Histology
A detailed histoanatomical study of the uropygial gland of fowl has already been described by Bhattacharyya (1972). It is a compound tubulo-alveolar holocrine gland, composed of parenchymal tissue. Generally two types of alveoli, viz. immature and mature, were found. However, unlike the fowl, in the chick immature types were abundant. 461 0016~6480/79/080461-05$01.00/O Copy! i&t &j 1979 by Academic Press. Inc. All rights of reproduction in any form reserved.
CHAKRABORTY,
462
MAITI,
AND BHATTACHARYYA
FIG. 1. A section of the uropygial gland from the untreated chick showing few mitotic cells (marked by arrow) only in the peripheral part of the alveoli. Masson’s stain (x600). FIG. 2. Note the hyperplasia (marked by arrow) in the uropygial gland following prolactin treatment (50 IU) in the chicks. Masson’s stain (x600).
change was noted in the aspect of the uropygial prolactin treatment in
quency of this gland to a significant level, (but there was no significantly different response between the two doses of the hormone) .
Mitotic Zncidence The dividing cells were generally located toward the basement membrane of the alveoli. These were found in moderate numbers in the untreated chicks (Fig. 1). Prolactin treatment (Fig. 2) in both low and high doses increased the mitotic fre-
Biochemical Analysis of Lipids Quantitative analysis revealed that in the normal juvenile chick the amount of total lipid comprised 21.81% of the fresh uropygial gland weight. Approximately 18.16% of the total lipid was separated as free fatty acids. The major fraction of the lipid was
No perceptible gross histological gland following chicks.
PROLACTIN
AND
CHICK
UROPYGIAL
GLAND
463
TABLE 1 COMPOSITIONOFTHE LIPIDSOFTHE UROPYGIALGLAND IN THE NORMAL AND THE PROLACTIN-TREATED CHICKS~ Compositions in total lipids of the gland Total wax
Diester wax Monoester wax
mg%
mg
mg%
mg
5.33 + 0.25
18.16 2 1.02
13.20 2 1.22
44.98 k 3.29
29.59 + 2.01
8.66 2 0.99
16.98 k 2.82
9.75 2 0.88
19.11 f 2.22
~0.01
60.10
~0.01
NS
164.65 k 7.39
36.00 * 2.99
21.86 -c 1.88
5.00 * 0.29
13.88 f 2.33
NS
NS
NS
NS
NS
Total lipid
Free fatty acids
Gland weight
mg
mg%
mg
A: Control: normal saline only
134.48’ k 5.33
29.34 5 2.41
21.81 2 1.90
B: Treated: 1.5 IU/bird daily for 10 days
172.33 f 8.78
51.00 + 4.33
NS
Group*
Probability C: Treated: 5 IUibird daily for 10 days Probability
co.05 3.20 -c 0.55
12.22 41.64 ++ 1.02 3.55 7.00 2 0.88
CO.01 co.05 8.88 k 1.01
mg%
2.90 -t 0.23
13.72 + 1.09
mg
mg%
1.00 2 0.08
3.40 2 0.21
2.75 f 0.25
5.39 f 0.39
co.05 ~0.001 co.02 8.05 * 1.29
0.30 + 0.02
0.83 k 0.05
a Three determinations were made for each sample. * Twenty birds in each group (10 specimens were used for lipid analysis and the remaining birds for mitotic studies). c Mean f SE
FIG. 3. The histogram showing percentages of mitotic, healthy, and pycnotic cells in the uropygial gland of the control and the prolactin-treated chicks. Note a rise in the mitotic frequency after prolactin treatment. The vertical bar represents the standard error of the mean value.
CHAKRABORTY,
464
MAITI,
AND
BHATTACHARYYA
lower dosage of prolactin, but decreased with the higher dosage (Table 1). -SOLVENT
Tz
TI
c
FRONT
s
FIG. 4. The photograph showing tic pattern of the wax alcohols from the uropygial glands of the control (C) and the prolactin-treated (T,, 15 IU; T,, 50 IU) chicks. Reference sample (S) contains highly pure (Sigma) hexadecanol (I), cholesterol (2), and butyl alcohol (3). Documentation: charring after 50% sulfuric acid spray.
identified as wax (44.98%). Out of the total wax, diester wax represented a major fraction (41.64% of the total lipid) in the chick uropygial gland. Monoester wax was recorded in negligible amounts (3.40% of the total lipid) (Table 1). Prolactin administration, in low dosage, increased the total lipid level of the uropygial gland, but the higher dosage failed to alter it. There was a drastic reduction in the weight of the total wax, particularly the diester fraction, obtained with both the dosages (Fig. 4, Table I), but it was observed more significantly with the higher dosage than with the lower dosage. The monoester wax level increased with the
DISCUSSION
Administration of mammalian (ovine) prolactin in the chicks evoked a rise in the incidence of mitosis of the uropygial gland, but simultaneously suppressed lipid production, particularly the wax fraction, which is the major component of the lipids of this gland (Gamo, 1971). But it is known that both cell proliferation (Maiti, 1968) and lipid production (Jacob, 1974) need to be maintained simultaneously for the normal functioning of this gland, since it is a lipidproducing holocrine gland. Thus, the present results indicate that prolactin possibly cannot stimulate the uropygial gland function. The present experiment with prolactin however, clarifies three points: (1) the luteotropin can at least “promote mitosis” of the uropygial gland of chicks; (2) it does not have a dose-dependent response with regard to mitosis as the latter was not increased in proportion to the amount of hormone administered (Fig. 3), but the dose-dependent response does exist in wax production which was diminished proportionately with the dosage of prolactin (Table 1); and (3) it has a dual role on both the cell proliferation and lipid production of the gland, as it stimulated the former but inhibited the latter event in the chick uropygial gland. Action of prolactin in the uropygial gland, however, differs from that of the sebaceous glands (cf. Shuster and Thody, 1974; Ebling et al., 1974). It is likely that it could be due to the difference in the species or the age of the animals employed, or to the variation in the source or dosage of the prolactin administered. ACKNOWLEDGMENTS This work was supported by a grant from the Special Assistance Programme of the University Grants Commission, Government of India, to the Department of Zoology, University of Calcutta. We wish to thank Professor Asok Ghosh. Sir Nilratan Sircar Professor
PROLACTIN
AND
CHICK
and Head of the Department of Zoology, University of Calcutta, for valuable advice.
REFERENCES Bhattacharyya, S. P. (1972). A comparative study on the histology and histochemistry of uropygial gland. Cellule 69, 113- 126. Bullough, W. S. (1962). The control of mitotic activity in adult mammalian tissue. Biol. Rev. 37, 301-342. Callahan, W. P. (1959). The effects of luteotrophin on sebaceous glands of the rat. Anat. Rec. 130, 281. Ebling, F. J. (1963). Hormonal control of sebaceous glands in experimental animals. In “Advances in Biology of Skin” (W. Montagna and R. Ellis, eds.), Chap. 13, pp. l-20. Pergamon, Oxford. Ebling, F. J., Ebling, E., Randall, J., and Skinner, J. (1975). The sebotrophic action of bovine growth hormone (BGH) in the rat. Brit. J. Dermatol. 92, 325-332. Ebling, F. J., Ebling, E., and Skinner, J. (1969). The influence of pituitary hormones on the response of sebaceous glands of male rats to testosterone. J. Endocrinol.
45, 245 - 256.
Edkins, E., and Hansen, I. A. (1972). Wax esters secreted by uropygial glands of some Australian water-fowls including magpie goose. Comp. Biochem. Physiol. 41B, 105-112. Folch, J., Lees, M., and Stanley, G. H. S. (1957). A simple method for the isolation and purification of total lipids from animal tissues. J. Biol. Chem. 266,497-509.
UROPYGIAL
GLAND
465
Gamo, M. (1971). The distribution of diol waxes in the preen glands of some birds. II. fnr. 1. Biochem. 2, 574-580. Jacob, J. (1975). TLC, GLC and M.S. of complex lipid mixtures from uropygial secretions. J. Chromatogr. Sri. 13, 415-422. Lorincz, A. L. (1963). The effects of progesterone and a pituitary preparation with sebotropic activity on sebaceous glands. In “Advances in Biology of Skin (W. Montagna, R. A. Ellis, and A. F. Silver, eds.), Vol. 4, pp. 188-199. Pergamon, Oxford. Mackenna, R. M. B., Wheatley, V. R., and Wormall, A. (1950). The composition of human surface skin fat (‘sebum’) from the human forearm. J. Znvesf. Dermatol.
15, 33-47.
Maiti, B. (1968). Cellular dynamics of the uropygial gland in the pigeon. Fuiia Bioi. (Krakow) 16, 49-54. Maiti, B. R., and Ghosh, A. (1972). Probable role of androgen in the regulation of the uropygial gland. Gen.
Comp.
Endocrinol.
19, 527-536.
Maiti, B. R., Bhattacharyya, S. P., and Ghosh, A. (1979). Hormonal regulation of the uropygial gland. Gen. Comp. Endocrinol. (communicated). Nikkari, T., and Valavaara, M. (1970). The effects of androgen and prolactin on the rate of production and composition of sebum in hypophysectomized female rats. J. Endocrinol. 48, 373-378. Shuster, S., and Thody, A. J. (1974). The control and measurement of sebum secretion. J. Invest. Dermarol. 62, 172- 190.
AND
COMPARATIVE
Action
38,461-465
ENDGCRINOLOGY
of Prolactin
on the Uropygial B.R.
SUBRATA~HAKRABORTY,* *Histophysiology Road, Calcutta
Laboratory, 7000/9. and
(1979)
Department tEndocrinology
MAITI,*
of Zoology, Laboratory, West Bengal,
Gland
AND S.P.
University Department India
of Chicks
BHATTACHARYYA?
of Calcutta, 35 Ballygunge of Zoology, University
Circular of Kalyani,
Accepted May 1, 1979 The aim of the present investigation was to ascertain the role of prolactin on the uropygial gland of chicks. The investigation was carried out by histological, karyodynamic, and biochemical studies. Ovine prolactin treatment in both low and high dosages increased the mitotic incidence but suppressed the wax content of the uropygial gland. It appears that although- prolactin can promote mitosis in the uropygial gland of chicks, it does not appear to _ stimulate the glandular function. gland (Maiti, 1968). The birds were killed by cervical dislocation 24 hr after the last injection of the hormone. The uropygial glands were dissected out, placed in Bouin’s fixative, and processed for histological and karyodynamic studies. Histological investigation was performed from the uropygial gland sections (5 pm) after staining with Masson’s technique. The karyodynamic investigation was carried out by staining the gland sections with iron-alum-hemotoxylin. Two thousand differential cells (viz., metaphase, healthy, and pycnotic) were counted at random from each gland for each bird and respective percentages of these cells were calculated. Total lipid content of the uropygial gland was estimated following the method of Folch et al. (1957). Free fatty acids were separated from total lipids following extraction with 0.5 N sodium hydroxide (Mackenna et al., 1950). Mono- and diester waxes of the glandular lipids were separated by column chromatography on silicic acid using cyclohexane and benzene as the solvent gradients (Jacob, 1975). Following saponification, corresponding wax alcohols were also analysed by thin layer chromatography on silica gel G-coated plates (Game, 1971) (Fig. 4). Benzene-ethyl acetate (9 : I v/v) was used as the solvent system for this purpose.
There are some indications that prolactin both directly stimulates the sebaceous glands and increases their response to testosterone and progesterone in intact or hypophysectomized rats (Callahan, 1959; Ebling e? al., 1969, 1975). But this has been disputed by others (Lorincz, 1963; Nikkari and Valavaara, 1970; Shuster and Thody, 1974) who did not find such action of prolactin in these rats. The avian uropygial gland resembles the sebaceous glands in structure, function, and hormonal regulation (Maiti and Ghosh, 1972; Maiti el al., 1979; cf. Ebling, 1963). But as yet the role of prolactin on the uropygial gland is not known. Thus it was investigated in the current paper. MATERIALS
AND METHODS
Fifteen-day-old male chicks (Leghorn) (body weight: between 70-80 g) were procured from a local poultry farm and maintained in uniform husbandry conditions in the laboratory with standard poultry feed and water ad libitum. Sixty birds were divided equally into three groups (viz., A, B, and C). The first group was kept for control and the remaining groups for hormone treatment. Purified ovine prolactin (NIH-LTH, USA) was dissolved in normal saline and injected intramuscularly in two dosages (see Table 1). Some of the birds belonging to both control and treated groups were injected intraperitoneally with colchicine (0.1 mg/lOO g body wt) at 6 hr prior to autopsy, for mitotic studies. The colchicine treatment was administered at the optimum time (10 PM to 4 AM) for obtaining maximum mitotic cells in the uropygial
RESULTS Gross Histology
A detailed histoanatomical study of the uropygial gland of fowl has already been described by Bhattacharyya (1972). It is a compound tubulo-alveolar holocrine gland, composed of parenchymal tissue. Generally two types of alveoli, viz. immature and mature, were found. However, unlike the fowl, in the chick immature types were abundant. 461 0016~6480/79/080461-05$01.00/O Copy! i&t &j 1979 by Academic Press. Inc. All rights of reproduction in any form reserved.
CHAKRABORTY,
462
MAITI,
AND BHATTACHARYYA
FIG. 1. A section of the uropygial gland from the untreated chick showing few mitotic cells (marked by arrow) only in the peripheral part of the alveoli. Masson’s stain (x600). FIG. 2. Note the hyperplasia (marked by arrow) in the uropygial gland following prolactin treatment (50 IU) in the chicks. Masson’s stain (x600).
change was noted in the aspect of the uropygial prolactin treatment in
quency of this gland to a significant level, (but there was no significantly different response between the two doses of the hormone) .
Mitotic Zncidence The dividing cells were generally located toward the basement membrane of the alveoli. These were found in moderate numbers in the untreated chicks (Fig. 1). Prolactin treatment (Fig. 2) in both low and high doses increased the mitotic fre-
Biochemical Analysis of Lipids Quantitative analysis revealed that in the normal juvenile chick the amount of total lipid comprised 21.81% of the fresh uropygial gland weight. Approximately 18.16% of the total lipid was separated as free fatty acids. The major fraction of the lipid was
No perceptible gross histological gland following chicks.
PROLACTIN
AND
CHICK
UROPYGIAL
GLAND
463
TABLE 1 COMPOSITIONOFTHE LIPIDSOFTHE UROPYGIALGLAND IN THE NORMAL AND THE PROLACTIN-TREATED CHICKS~ Compositions in total lipids of the gland Total wax
Diester wax Monoester wax
mg%
mg
mg%
mg
5.33 + 0.25
18.16 2 1.02
13.20 2 1.22
44.98 k 3.29
29.59 + 2.01
8.66 2 0.99
16.98 k 2.82
9.75 2 0.88
19.11 f 2.22
~0.01
60.10
~0.01
NS
164.65 k 7.39
36.00 * 2.99
21.86 -c 1.88
5.00 * 0.29
13.88 f 2.33
NS
NS
NS
NS
NS
Total lipid
Free fatty acids
Gland weight
mg
mg%
mg
A: Control: normal saline only
134.48’ k 5.33
29.34 5 2.41
21.81 2 1.90
B: Treated: 1.5 IU/bird daily for 10 days
172.33 f 8.78
51.00 + 4.33
NS
Group*
Probability C: Treated: 5 IUibird daily for 10 days Probability
co.05 3.20 -c 0.55
12.22 41.64 ++ 1.02 3.55 7.00 2 0.88
CO.01 co.05 8.88 k 1.01
mg%
2.90 -t 0.23
13.72 + 1.09
mg
mg%
1.00 2 0.08
3.40 2 0.21
2.75 f 0.25
5.39 f 0.39
co.05 ~0.001 co.02 8.05 * 1.29
0.30 + 0.02
0.83 k 0.05
a Three determinations were made for each sample. * Twenty birds in each group (10 specimens were used for lipid analysis and the remaining birds for mitotic studies). c Mean f SE
FIG. 3. The histogram showing percentages of mitotic, healthy, and pycnotic cells in the uropygial gland of the control and the prolactin-treated chicks. Note a rise in the mitotic frequency after prolactin treatment. The vertical bar represents the standard error of the mean value.
CHAKRABORTY,
464
MAITI,
AND
BHATTACHARYYA
lower dosage of prolactin, but decreased with the higher dosage (Table 1). -SOLVENT
Tz
TI
c
FRONT
s
FIG. 4. The photograph showing tic pattern of the wax alcohols from the uropygial glands of the control (C) and the prolactin-treated (T,, 15 IU; T,, 50 IU) chicks. Reference sample (S) contains highly pure (Sigma) hexadecanol (I), cholesterol (2), and butyl alcohol (3). Documentation: charring after 50% sulfuric acid spray.
identified as wax (44.98%). Out of the total wax, diester wax represented a major fraction (41.64% of the total lipid) in the chick uropygial gland. Monoester wax was recorded in negligible amounts (3.40% of the total lipid) (Table 1). Prolactin administration, in low dosage, increased the total lipid level of the uropygial gland, but the higher dosage failed to alter it. There was a drastic reduction in the weight of the total wax, particularly the diester fraction, obtained with both the dosages (Fig. 4, Table I), but it was observed more significantly with the higher dosage than with the lower dosage. The monoester wax level increased with the
DISCUSSION
Administration of mammalian (ovine) prolactin in the chicks evoked a rise in the incidence of mitosis of the uropygial gland, but simultaneously suppressed lipid production, particularly the wax fraction, which is the major component of the lipids of this gland (Gamo, 1971). But it is known that both cell proliferation (Maiti, 1968) and lipid production (Jacob, 1974) need to be maintained simultaneously for the normal functioning of this gland, since it is a lipidproducing holocrine gland. Thus, the present results indicate that prolactin possibly cannot stimulate the uropygial gland function. The present experiment with prolactin however, clarifies three points: (1) the luteotropin can at least “promote mitosis” of the uropygial gland of chicks; (2) it does not have a dose-dependent response with regard to mitosis as the latter was not increased in proportion to the amount of hormone administered (Fig. 3), but the dose-dependent response does exist in wax production which was diminished proportionately with the dosage of prolactin (Table 1); and (3) it has a dual role on both the cell proliferation and lipid production of the gland, as it stimulated the former but inhibited the latter event in the chick uropygial gland. Action of prolactin in the uropygial gland, however, differs from that of the sebaceous glands (cf. Shuster and Thody, 1974; Ebling et al., 1974). It is likely that it could be due to the difference in the species or the age of the animals employed, or to the variation in the source or dosage of the prolactin administered. ACKNOWLEDGMENTS This work was supported by a grant from the Special Assistance Programme of the University Grants Commission, Government of India, to the Department of Zoology, University of Calcutta. We wish to thank Professor Asok Ghosh. Sir Nilratan Sircar Professor
PROLACTIN
AND
CHICK
and Head of the Department of Zoology, University of Calcutta, for valuable advice.
REFERENCES Bhattacharyya, S. P. (1972). A comparative study on the histology and histochemistry of uropygial gland. Cellule 69, 113- 126. Bullough, W. S. (1962). The control of mitotic activity in adult mammalian tissue. Biol. Rev. 37, 301-342. Callahan, W. P. (1959). The effects of luteotrophin on sebaceous glands of the rat. Anat. Rec. 130, 281. Ebling, F. J. (1963). Hormonal control of sebaceous glands in experimental animals. In “Advances in Biology of Skin” (W. Montagna and R. Ellis, eds.), Chap. 13, pp. l-20. Pergamon, Oxford. Ebling, F. J., Ebling, E., Randall, J., and Skinner, J. (1975). The sebotrophic action of bovine growth hormone (BGH) in the rat. Brit. J. Dermatol. 92, 325-332. Ebling, F. J., Ebling, E., and Skinner, J. (1969). The influence of pituitary hormones on the response of sebaceous glands of male rats to testosterone. J. Endocrinol.
45, 245 - 256.
Edkins, E., and Hansen, I. A. (1972). Wax esters secreted by uropygial glands of some Australian water-fowls including magpie goose. Comp. Biochem. Physiol. 41B, 105-112. Folch, J., Lees, M., and Stanley, G. H. S. (1957). A simple method for the isolation and purification of total lipids from animal tissues. J. Biol. Chem. 266,497-509.
UROPYGIAL
GLAND
465
Gamo, M. (1971). The distribution of diol waxes in the preen glands of some birds. II. fnr. 1. Biochem. 2, 574-580. Jacob, J. (1975). TLC, GLC and M.S. of complex lipid mixtures from uropygial secretions. J. Chromatogr. Sri. 13, 415-422. Lorincz, A. L. (1963). The effects of progesterone and a pituitary preparation with sebotropic activity on sebaceous glands. In “Advances in Biology of Skin (W. Montagna, R. A. Ellis, and A. F. Silver, eds.), Vol. 4, pp. 188-199. Pergamon, Oxford. Mackenna, R. M. B., Wheatley, V. R., and Wormall, A. (1950). The composition of human surface skin fat (‘sebum’) from the human forearm. J. Znvesf. Dermatol.
15, 33-47.
Maiti, B. (1968). Cellular dynamics of the uropygial gland in the pigeon. Fuiia Bioi. (Krakow) 16, 49-54. Maiti, B. R., and Ghosh, A. (1972). Probable role of androgen in the regulation of the uropygial gland. Gen.
Comp.
Endocrinol.
19, 527-536.
Maiti, B. R., Bhattacharyya, S. P., and Ghosh, A. (1979). Hormonal regulation of the uropygial gland. Gen. Comp. Endocrinol. (communicated). Nikkari, T., and Valavaara, M. (1970). The effects of androgen and prolactin on the rate of production and composition of sebum in hypophysectomized female rats. J. Endocrinol. 48, 373-378. Shuster, S., and Thody, A. J. (1974). The control and measurement of sebum secretion. J. Invest. Dermarol. 62, 172- 190.