- Email: [email protected]
Comparison of mild vs severe pressure overload on the enzymatic activity of myosin in the canine ventricles
BIOCHEMICAL
MEDICINE
14, 139-146
(1975)
Comparison of Mild vs Severe Pressure Overload on the Enzymatic Activity of Myosin in the Canine Ventricles JOAN WIKMAN-COFFELT, ANTONE SALEL, TEIKO
CLAUDIA FENNER, ROBERT WALSH, KAMIYAMA, AND DEAN T. MASON
Section of Cardiovuscular University of California, Received
Medicine, Department of Medicine, Davis. School of Medicine 95616 August
1. 1975
INTRODUCTION
It was demonstrated by Meet-son er al. (1) that cardiac myosin ATPase activity was elevated during early stages following pulmonic stenosis. Earlier studies carried out in our laboratories were consistent with this work. Right ventricular myosin ATPase activity was elevated during early stages following mild pulmonic stenosis; this elevation was related to the proportion of myosin light chains present (2, 3). A low myosin and myofibrillar ATPase activity has been reported in several models of cardiac dysfunction (4,7), including severe aortic stenosis (8). The decrease in left ventricular myosin ATPase activity observed was related to the proportion of myosin light chains present, and this, in turn, was reflected in the number of calcium binding sites (8). In the work reported here, it is shown that the ATPase activity of myosin in the pressure overloaded ventricle varied depending on both the degree of banding and the time after banding. PROCEDURES
Severe systolic pressure overload of the right ventricle was induced by using an inflatable Jacobson cuff as described by Bishop and Cole (9). Mild banding of the pulmonary artery was described earlier (2, 3). Measurements of cardiac hemodynamics were carried out under light pentobarbital anesthesia by the methods described earlier (10). Mild and severe aortic stenosis were induced by banding the ascending aorta (8). Previously we developed a procedure for purification of canine myocardial myosin by which it was possible to obtain electrophoretically and immunologically pure myosin with high enzymatic activity (11-13). Myosin ATPase activity varied with the temperature at which it was assayed (Table 1). In the studies described here myosin was analyzed at 37”. To obtain myosin from cardiac ventricles, only the free wall of the chambers was used; the septum was not analyzed. 139 Copyright All right>
c: 1975 by Academic Pres. of reproduction in any form
Inc. rexwed.
140
WIKMAN-COFFELT
MY~SIN
ENZYMATIC
V,,,,,
E-I
TABLE I RELATIVE
VALUES
(right K’ Temperature of assay
AL.
TO INCUBAIXON
TEMPFAATURES _I_-__
Normal ventricle)
Activated ~‘,,u,, wmoles
25”
myosin enzymatic Values PO,/mg/min)
0.57 0.72
27” 30” 32”
I .05 1 .?O
35” 37”
I .68 2.03 -
’ The enzymatic Assays were linear
V,,, with
values time.
of myosin
varied
with
temperature
at which
it was
assayed.
Optimal parameters were established for studying the kinetics of myosin using monovalent or divalent cations as single effecters (11). Conditions for analyzing myosin ATPase activity were described in earlier reports (2, 11). Each analysis described here was repeated on six test animals. Student’s t-test, either paired or unpaired, was used in comparisons. In all analyses, a probability level of 0.05 was the criterion of significance. RESULTS
The averages of right ventricular peak systolic pressure were: normal dogs, 20.9 t 3.7 mm Hg; dogs killed after 5 weeks of mild pulmonic stenosis, 32.0 + 2.8 mm Hg; and dogs killed after 6 weeks of severe pulmonary artery banding, 68.8 ? 5 mm Hg. As in the right ventricle following mild pulmonic stenosis (13) there was a significant increase (P < 0.001) in the weight of the hypertrophied right ventricles following severe pulmonic stenosis; the hypertrophied right ventricle weights (free wall) relative to body weights in grams x 1O-“, after 5 weeks of severe pulmonic banding, were 1.13 + 0.11; normal right ventricle values were 0.71 i 0.08. Right ventricular myosin following severe pulmonic stenosis was similar in electrophoretic mobility and purity to that of control animals and animals subject to mild pulmonic stenosis (2). In all cases the experimental animals exhibited no clinical manifestations of heart failure, i.e., ascites, pleural effusion, perpheral edema, or dyspnea, and according to clinical appearance could not be differentiated from the normal control. The K+ and Ca*+ enzymatic V,,, values of left ventricular myosin were 25-30% higher than those of right ventricular myosin as shown earlier (8). and repeated here under varying conditions (Table 2). Following mild
MYOSIN
AVERAGE
IN THE CANINE
ENZYMATIC
141
VENTRICLES
TABLE 2 V,,,,, VALUES
OF MYOSK+~
Activator cation
Left ventricle
Right ventricle
Kf Caz+ NH‘+
SE 2.84 2 0.17 0.97 2 0.14 7.20 2 0.30
SE 2.05 -r- 0.15* 0.72 -+ 0.09* 7.28 -+ 0.24c
n kmoles POJmg/min. btl=6. r (ND) No Difference. * (p .OOl).
pulmonic stenosis, the K+ and Ca2+. enzymatic activities of right ventricular myosin were elevated (Table 3). By 16 weeks after surgery, the enzymatic activities had returned to near normal values (Table 3). K+ and Ca*+ activated myosin enzymatic V,,, values were never elevated, but were significantly decreased in the right ventricles following severe pulmonary artery banding (Table 3). The first significant deviations from normal right ventricular myosin ATPase activities were detected 5 weeks after inflating the Jacobson cuff. At this time, myosin activity was significantly decreased (12%) from those of normal values; this was a similar postoperative time when myosin ATPase activity reached maximum enzymatic V,,, values in dogs subject to mild pulmonic stenosis. With NH+ as the activator cation the enzymatic activity of myosin (11, 13) was the same in the normal ventricles as compared to data obtained from either ventricles of 5 weeks postoperative dogs with mild pulmonic stenosis, or from animals killed after 5 weeks of severe pulmonary artery banding (Table 3). Left ventricular myosin from normal animals, from animals following 5 and 12 weeks of mild aortic stenosis, and also 5 and 12 weeks of severe aortic stenosis gave similar patterns on polyacrylamide gels after electrophoresis. In recent reports it was shown that K+ and Ca*+ activated myosin enzymatic V,,, values were decreased during severe aortic stenosis (8), whereas NH,+ activated myosin V,, values were the same (8). Mild aortic stenosis was performed by banding the ascending aorta, affecting a transaortic peak systolic pressure gradient of 25 mm Hg. Under these conditions, as in severe aortic stenosis (8), the left ventricle hypertrophied. With 5 weeks of mild aortic stenosis, the left ventricle weights relative to body weights in grams x 1t3 were 1.91 & 0.10. The normal values for the free wall of the left ventricle relative to body weight were 1.50 rfr 0.05. As in mild pulmonic stenosis, mild aortic stenosis caused an elevation in K+ and Ca*+ activated myosin enzymatic V,,, values by 5 weeks after
MYOSIN
IN
THE
CANINE
VENTRICLES
143
surgery, which then returned to near normal values following 12 weeks of mild pressure overload (Table 4). In severe aortic stenosis, left ventricular myosin ATPase activity was never elevated, but was normal after 2 weeks of severe pressure overload; the activity then decreased to 15% below normal after 5 weeks of severe pressure overload (8), and 27% below normal after 12 weeks of severe pressure overload (Table 4). In all four types of cases presented here, data are not shown, the nonbanded ventricle, hemodynamically nonstressed ventricle, hypertrophied; also, the K+ activated myosin ATPase activity was elevated. These changes were detectable only after a time period of 3 to 4 months following surgery. In both mild and severe pulmonic stenosis, the right ventricle hypertrophied, but to a lesser extent when the pressure overload was mild. The weight of the free wall of the normal right ventricle relative to body weight in grams x 1C3 was 0.71. With 5 weeks of mild pulmonic stenosis it was 1.06 (3), and with 5 weeks of severe pulmonic stenosis, as reported here, it was 1.13. Likewise, both in mild and severe aortic stenosis, the left ventricle hypertrophied, but to a lesser degree when the pressure overload was mild as compared to when it was severe. The weight of the free wall of the normal left ventricle relative to body weight in grams x 1w3 was 1.50. With 5 weeks of mild aortic stenosis, as reported here, it was 1.91; and with 5 weeks of severe aortic stenosis it was 2.20 (8). DISCUSSION
A mild pressure overload caused an elevation in myosin ATPase activity, whereas a severe pressure overload caused a depression in the enzymatic V maz values of myosin. The changes observed in myosin induced by a pressure overload were slow in occurring. The first significant alterations in myosin activity from normal values occurred after 3 weeks of an increased pressure overload on the stressed ventricle (8). After applying an increased pressure load, mild or severe, on either ventricle, left or right, by aortic or pulmonic banding, myosin from either of the two hemodynamically stressed ventricles had dissimilar enzymatic activity from that of the control. Myosin from the ventricle to which pressure was applied was elevated in ATPase activity if banding was mild and depressed if banding was severe, but the hemodynamically nonstressed ventricle was latent in responding. In all cases, by 12 weeks after surgery the hemodynamically nonstressed ventricle was elevated in K+ activated enzymatic V,,, values. The myosin purified and analyzed from the hemodynamically stressed ventricles had alterations in chain proportions and calcium binding (2, 8, 14). Associated with an increase in the enzymatic V,,,,, values of myosin there were less moles of light chains per mole of myosin and a lesser number of calcium binding sites (8, 14). The converse was also true, with a
E
min
2.84 + 0.17 0.97 t 0.14 7.20 f 0.30
K’ Ca!NtZ’
” ~moles PO,/mg “n=6. ’ (ND). + P <: 0.01. ‘* P -c 0.05. *** P < 0.001.
Normal left ventricle
.Activator cation 3.12 i 0.08* 1.10 + 0.10* 7.27 2 0.19
(5 weeks) (SE)
V,,,,
stenosis
Enzymatic
Mild
Hypertrophied
of left ventricular
2.80 i 0.11’ 0.98 I [email protected] i 0.30
(12 weeks) (SE)
values
TABLE 4 AORTIC STENOSIS
2.70 0.88 7.34
-+ 0.14** i O.l?*’ f 0.16
(5 weeks) (SE)
left ventricle
myosin”,”
Severe
stenosis
1.75 t o.ll”*’ 0.62 -t O.ll**’ 7.27 i. 0.24r
(13 weeks) (SE)
-
MYOSIN
IN
THE
CANINE
VENTRICLES
145
decrease in the enzymatic V,,,,, values of myosin there were a greater number of moles of light chains per mole of myosin and a greater number of calcium binding sites (8, 14). SUMMARY
Mild pulmonic stenosis, performed in dogs by banding the pulmonary artery, elevated right ventricular peak systolic pressure to 60% above the control; this resulted in an elevation in right ventricular K+ and Caz+ activated myosin ATPase activities which peaked (35% above normal) in In contrast, severe enzymatic V,,, values by 5 weeks postoperatively. pulmonic stenosis produced by the inflatable Jacobson cuff, elevating right ventricular peak systolic pressure to 300% above the control, did not produce an increase in myosin enzymatic ATPase V,,,,, values. The first significant deviation from normal myosin ATPase activity was detected after 5 weeks of severe pulmonic stenosis; at this time right ventricular myosin enzymatic V,,, values were depressed significantly from those of normal values by 12%. (NH+ activated myosin V,,, value remained normal). Likewise mild aortic stenosis, induced by banding the ascending aorta, forcing a transaortic pressure gradient of 25 mm Hg, caused a 15% elevation in left ventricular myosin ATPase activities by 5 weeks after operation; myosin enzymatic V,,, values decreased to normal values by 12 weeks after surgery. Severe aortic stenosis, brought about by creating a transaortic pressure gradient of 55 mm Hg, never caused an elevation in left ventricular myosin enzymatic V,,, values, but caused a 15% decrease in K+ and Caz+ activated myosin by 5 weeks after operation and a decrease to 28% below normal by 12 weeks of pressure overload. ACKNOWLEDGMENTS This study was supported by Research Program Project Grant HL-14780 and AM-NS16716-01 AMP, from the National Institutes of Health, and the American Heart Association (Golden Empire Chapter).
REFERENCES 1. Meerson, F. Z., Circ. Res. (SuppI. II) 24, 115 (1969). 2. Wikman-Coffelt, J., Fenner, C., Lotysh, M., McPherson, J., Zelis, R., and Mason, D. T., J. Molec. Cell. Cardiol. 7, 513 (1975). 3. Wikman-Coffelt, J., Fenner, C., Coffelt, R., and Mason, D. T., J. Molec. Cell. Curdiol. 7, 219 (1975). 4. Alpert, N. R., Hamrell, B. B., and Halpern. W., Circ. Res. 34 and 35, (II-7lHII-81) (1974). 5. Chandler, B. M., Sonnenblick, E. H., Spann, J. F., and Pool, P. E., Circ. Res. 21, 717 (1967). 6. Nebel, M. L., and Bing, R. J., Arch. Intern. Med. 111, 190 (1963). 7. Oganessyan, S., Zaminian, T., Bay, N., Petrosian, V., Koschkarian. A., Martirosian. I., and Eloyan, M., J. Molec. Cell. Cardiol. 5, 1 (1973). 8. Wikman-Coffelt, J., Fenner, C., Zelis, R., and Mason, D. T., J. Biol. Chem. 250:1257 (1975).
146
WIKMAN-COFFEIX
9. Bishop. S. P., and Cole. C. K.. J. Appl. 10. Zelis. R.. Wikman-Coffelt. J.. Kamiyama. and Mason, D. T., in “Myocardiology” sity Park Press, Baltimore, Maryland, I I. Fenner. C.. Mason, D. T., Zelis, R., and A. 70, 3205 (1973). 12. Wikman-Coffelt. J.. Zelis, R.. Fenner. (1973). 13. Wikman-Coffelt, J., Zelis. R.. Fenner, Commrrn. 51, 1097 (1973). 14. Wikman-Coffelt. J.. Smith. A., Walsh, Mason. D. T., J. :Uolec. Cell. Crrrdiol.
ET AL. Ph?;~;d.
26,
659
(1969).
T.. Peng. C. L., Salel. A. F.. Amsterdam, E.. (E. Bajusz. Ed.). Vol. 3, pp. 625-635. Univer1973. Wikman-Coffelt, J.. Prcw Vr,r. ~c,id. .Yc,r. c:. .Y c‘.. and Mason. C., and Mason. R.. Fenner. (In presy).
D. T.. Prel~.
Bl<,chern.
I>. T.. Biochew~.
C.. Kamiyama,
T..
3. 339
Bi0phy.c. Salel,
Re.5.
A.. and
MEDICINE
14, 139-146
(1975)
Comparison of Mild vs Severe Pressure Overload on the Enzymatic Activity of Myosin in the Canine Ventricles JOAN WIKMAN-COFFELT, ANTONE SALEL, TEIKO
CLAUDIA FENNER, ROBERT WALSH, KAMIYAMA, AND DEAN T. MASON
Section of Cardiovuscular University of California, Received
Medicine, Department of Medicine, Davis. School of Medicine 95616 August
1. 1975
INTRODUCTION
It was demonstrated by Meet-son er al. (1) that cardiac myosin ATPase activity was elevated during early stages following pulmonic stenosis. Earlier studies carried out in our laboratories were consistent with this work. Right ventricular myosin ATPase activity was elevated during early stages following mild pulmonic stenosis; this elevation was related to the proportion of myosin light chains present (2, 3). A low myosin and myofibrillar ATPase activity has been reported in several models of cardiac dysfunction (4,7), including severe aortic stenosis (8). The decrease in left ventricular myosin ATPase activity observed was related to the proportion of myosin light chains present, and this, in turn, was reflected in the number of calcium binding sites (8). In the work reported here, it is shown that the ATPase activity of myosin in the pressure overloaded ventricle varied depending on both the degree of banding and the time after banding. PROCEDURES
Severe systolic pressure overload of the right ventricle was induced by using an inflatable Jacobson cuff as described by Bishop and Cole (9). Mild banding of the pulmonary artery was described earlier (2, 3). Measurements of cardiac hemodynamics were carried out under light pentobarbital anesthesia by the methods described earlier (10). Mild and severe aortic stenosis were induced by banding the ascending aorta (8). Previously we developed a procedure for purification of canine myocardial myosin by which it was possible to obtain electrophoretically and immunologically pure myosin with high enzymatic activity (11-13). Myosin ATPase activity varied with the temperature at which it was assayed (Table 1). In the studies described here myosin was analyzed at 37”. To obtain myosin from cardiac ventricles, only the free wall of the chambers was used; the septum was not analyzed. 139 Copyright All right>
c: 1975 by Academic Pres. of reproduction in any form
Inc. rexwed.
140
WIKMAN-COFFELT
MY~SIN
ENZYMATIC
V,,,,,
E-I
TABLE I RELATIVE
VALUES
(right K’ Temperature of assay
AL.
TO INCUBAIXON
TEMPFAATURES _I_-__
Normal ventricle)
Activated ~‘,,u,, wmoles
25”
myosin enzymatic Values PO,/mg/min)
0.57 0.72
27” 30” 32”
I .05 1 .?O
35” 37”
I .68 2.03 -
’ The enzymatic Assays were linear
V,,, with
values time.
of myosin
varied
with
temperature
at which
it was
assayed.
Optimal parameters were established for studying the kinetics of myosin using monovalent or divalent cations as single effecters (11). Conditions for analyzing myosin ATPase activity were described in earlier reports (2, 11). Each analysis described here was repeated on six test animals. Student’s t-test, either paired or unpaired, was used in comparisons. In all analyses, a probability level of 0.05 was the criterion of significance. RESULTS
The averages of right ventricular peak systolic pressure were: normal dogs, 20.9 t 3.7 mm Hg; dogs killed after 5 weeks of mild pulmonic stenosis, 32.0 + 2.8 mm Hg; and dogs killed after 6 weeks of severe pulmonary artery banding, 68.8 ? 5 mm Hg. As in the right ventricle following mild pulmonic stenosis (13) there was a significant increase (P < 0.001) in the weight of the hypertrophied right ventricles following severe pulmonic stenosis; the hypertrophied right ventricle weights (free wall) relative to body weights in grams x 1O-“, after 5 weeks of severe pulmonic banding, were 1.13 + 0.11; normal right ventricle values were 0.71 i 0.08. Right ventricular myosin following severe pulmonic stenosis was similar in electrophoretic mobility and purity to that of control animals and animals subject to mild pulmonic stenosis (2). In all cases the experimental animals exhibited no clinical manifestations of heart failure, i.e., ascites, pleural effusion, perpheral edema, or dyspnea, and according to clinical appearance could not be differentiated from the normal control. The K+ and Ca*+ enzymatic V,,, values of left ventricular myosin were 25-30% higher than those of right ventricular myosin as shown earlier (8). and repeated here under varying conditions (Table 2). Following mild
MYOSIN
AVERAGE
IN THE CANINE
ENZYMATIC
141
VENTRICLES
TABLE 2 V,,,,, VALUES
OF MYOSK+~
Activator cation
Left ventricle
Right ventricle
Kf Caz+ NH‘+
SE 2.84 2 0.17 0.97 2 0.14 7.20 2 0.30
SE 2.05 -r- 0.15* 0.72 -+ 0.09* 7.28 -+ 0.24c
n kmoles POJmg/min. btl=6. r (ND) No Difference. * (p .OOl).
pulmonic stenosis, the K+ and Ca2+. enzymatic activities of right ventricular myosin were elevated (Table 3). By 16 weeks after surgery, the enzymatic activities had returned to near normal values (Table 3). K+ and Ca*+ activated myosin enzymatic V,,, values were never elevated, but were significantly decreased in the right ventricles following severe pulmonary artery banding (Table 3). The first significant deviations from normal right ventricular myosin ATPase activities were detected 5 weeks after inflating the Jacobson cuff. At this time, myosin activity was significantly decreased (12%) from those of normal values; this was a similar postoperative time when myosin ATPase activity reached maximum enzymatic V,,, values in dogs subject to mild pulmonic stenosis. With NH+ as the activator cation the enzymatic activity of myosin (11, 13) was the same in the normal ventricles as compared to data obtained from either ventricles of 5 weeks postoperative dogs with mild pulmonic stenosis, or from animals killed after 5 weeks of severe pulmonary artery banding (Table 3). Left ventricular myosin from normal animals, from animals following 5 and 12 weeks of mild aortic stenosis, and also 5 and 12 weeks of severe aortic stenosis gave similar patterns on polyacrylamide gels after electrophoresis. In recent reports it was shown that K+ and Ca*+ activated myosin enzymatic V,,, values were decreased during severe aortic stenosis (8), whereas NH,+ activated myosin V,, values were the same (8). Mild aortic stenosis was performed by banding the ascending aorta, affecting a transaortic peak systolic pressure gradient of 25 mm Hg. Under these conditions, as in severe aortic stenosis (8), the left ventricle hypertrophied. With 5 weeks of mild aortic stenosis, the left ventricle weights relative to body weights in grams x 1t3 were 1.91 & 0.10. The normal values for the free wall of the left ventricle relative to body weight were 1.50 rfr 0.05. As in mild pulmonic stenosis, mild aortic stenosis caused an elevation in K+ and Ca*+ activated myosin enzymatic V,,, values by 5 weeks after
MYOSIN
IN
THE
CANINE
VENTRICLES
143
surgery, which then returned to near normal values following 12 weeks of mild pressure overload (Table 4). In severe aortic stenosis, left ventricular myosin ATPase activity was never elevated, but was normal after 2 weeks of severe pressure overload; the activity then decreased to 15% below normal after 5 weeks of severe pressure overload (8), and 27% below normal after 12 weeks of severe pressure overload (Table 4). In all four types of cases presented here, data are not shown, the nonbanded ventricle, hemodynamically nonstressed ventricle, hypertrophied; also, the K+ activated myosin ATPase activity was elevated. These changes were detectable only after a time period of 3 to 4 months following surgery. In both mild and severe pulmonic stenosis, the right ventricle hypertrophied, but to a lesser extent when the pressure overload was mild. The weight of the free wall of the normal right ventricle relative to body weight in grams x 1C3 was 0.71. With 5 weeks of mild pulmonic stenosis it was 1.06 (3), and with 5 weeks of severe pulmonic stenosis, as reported here, it was 1.13. Likewise, both in mild and severe aortic stenosis, the left ventricle hypertrophied, but to a lesser degree when the pressure overload was mild as compared to when it was severe. The weight of the free wall of the normal left ventricle relative to body weight in grams x 1w3 was 1.50. With 5 weeks of mild aortic stenosis, as reported here, it was 1.91; and with 5 weeks of severe aortic stenosis it was 2.20 (8). DISCUSSION
A mild pressure overload caused an elevation in myosin ATPase activity, whereas a severe pressure overload caused a depression in the enzymatic V maz values of myosin. The changes observed in myosin induced by a pressure overload were slow in occurring. The first significant alterations in myosin activity from normal values occurred after 3 weeks of an increased pressure overload on the stressed ventricle (8). After applying an increased pressure load, mild or severe, on either ventricle, left or right, by aortic or pulmonic banding, myosin from either of the two hemodynamically stressed ventricles had dissimilar enzymatic activity from that of the control. Myosin from the ventricle to which pressure was applied was elevated in ATPase activity if banding was mild and depressed if banding was severe, but the hemodynamically nonstressed ventricle was latent in responding. In all cases, by 12 weeks after surgery the hemodynamically nonstressed ventricle was elevated in K+ activated enzymatic V,,, values. The myosin purified and analyzed from the hemodynamically stressed ventricles had alterations in chain proportions and calcium binding (2, 8, 14). Associated with an increase in the enzymatic V,,,,, values of myosin there were less moles of light chains per mole of myosin and a lesser number of calcium binding sites (8, 14). The converse was also true, with a
E
min
2.84 + 0.17 0.97 t 0.14 7.20 f 0.30
K’ Ca!NtZ’
” ~moles PO,/mg “n=6. ’ (ND). + P <: 0.01. ‘* P -c 0.05. *** P < 0.001.
Normal left ventricle
.Activator cation 3.12 i 0.08* 1.10 + 0.10* 7.27 2 0.19
(5 weeks) (SE)
V,,,,
stenosis
Enzymatic
Mild
Hypertrophied
of left ventricular
2.80 i 0.11’ 0.98 I [email protected] i 0.30
(12 weeks) (SE)
values
TABLE 4 AORTIC STENOSIS
2.70 0.88 7.34
-+ 0.14** i O.l?*’ f 0.16
(5 weeks) (SE)
left ventricle
myosin”,”
Severe
stenosis
1.75 t o.ll”*’ 0.62 -t O.ll**’ 7.27 i. 0.24r
(13 weeks) (SE)
-
MYOSIN
IN
THE
CANINE
VENTRICLES
145
decrease in the enzymatic V,,,,, values of myosin there were a greater number of moles of light chains per mole of myosin and a greater number of calcium binding sites (8, 14). SUMMARY
Mild pulmonic stenosis, performed in dogs by banding the pulmonary artery, elevated right ventricular peak systolic pressure to 60% above the control; this resulted in an elevation in right ventricular K+ and Caz+ activated myosin ATPase activities which peaked (35% above normal) in In contrast, severe enzymatic V,,, values by 5 weeks postoperatively. pulmonic stenosis produced by the inflatable Jacobson cuff, elevating right ventricular peak systolic pressure to 300% above the control, did not produce an increase in myosin enzymatic ATPase V,,,,, values. The first significant deviation from normal myosin ATPase activity was detected after 5 weeks of severe pulmonic stenosis; at this time right ventricular myosin enzymatic V,,, values were depressed significantly from those of normal values by 12%. (NH+ activated myosin V,,, value remained normal). Likewise mild aortic stenosis, induced by banding the ascending aorta, forcing a transaortic pressure gradient of 25 mm Hg, caused a 15% elevation in left ventricular myosin ATPase activities by 5 weeks after operation; myosin enzymatic V,,, values decreased to normal values by 12 weeks after surgery. Severe aortic stenosis, brought about by creating a transaortic pressure gradient of 55 mm Hg, never caused an elevation in left ventricular myosin enzymatic V,,, values, but caused a 15% decrease in K+ and Caz+ activated myosin by 5 weeks after operation and a decrease to 28% below normal by 12 weeks of pressure overload. ACKNOWLEDGMENTS This study was supported by Research Program Project Grant HL-14780 and AM-NS16716-01 AMP, from the National Institutes of Health, and the American Heart Association (Golden Empire Chapter).
REFERENCES 1. Meerson, F. Z., Circ. Res. (SuppI. II) 24, 115 (1969). 2. Wikman-Coffelt, J., Fenner, C., Lotysh, M., McPherson, J., Zelis, R., and Mason, D. T., J. Molec. Cell. Cardiol. 7, 513 (1975). 3. Wikman-Coffelt, J., Fenner, C., Coffelt, R., and Mason, D. T., J. Molec. Cell. Curdiol. 7, 219 (1975). 4. Alpert, N. R., Hamrell, B. B., and Halpern. W., Circ. Res. 34 and 35, (II-7lHII-81) (1974). 5. Chandler, B. M., Sonnenblick, E. H., Spann, J. F., and Pool, P. E., Circ. Res. 21, 717 (1967). 6. Nebel, M. L., and Bing, R. J., Arch. Intern. Med. 111, 190 (1963). 7. Oganessyan, S., Zaminian, T., Bay, N., Petrosian, V., Koschkarian. A., Martirosian. I., and Eloyan, M., J. Molec. Cell. Cardiol. 5, 1 (1973). 8. Wikman-Coffelt, J., Fenner, C., Zelis, R., and Mason, D. T., J. Biol. Chem. 250:1257 (1975).
146
WIKMAN-COFFEIX
9. Bishop. S. P., and Cole. C. K.. J. Appl. 10. Zelis. R.. Wikman-Coffelt. J.. Kamiyama. and Mason, D. T., in “Myocardiology” sity Park Press, Baltimore, Maryland, I I. Fenner. C.. Mason, D. T., Zelis, R., and A. 70, 3205 (1973). 12. Wikman-Coffelt. J.. Zelis, R.. Fenner. (1973). 13. Wikman-Coffelt, J., Zelis. R.. Fenner, Commrrn. 51, 1097 (1973). 14. Wikman-Coffelt. J.. Smith. A., Walsh, Mason. D. T., J. :Uolec. Cell. Crrrdiol.
ET AL. Ph?;~;d.
26,
659
(1969).
T.. Peng. C. L., Salel. A. F.. Amsterdam, E.. (E. Bajusz. Ed.). Vol. 3, pp. 625-635. Univer1973. Wikman-Coffelt, J.. Prcw Vr,r. ~c,id. .Yc,r. c:. .Y c‘.. and Mason. C., and Mason. R.. Fenner. (In presy).
D. T.. Prel~.
Bl<,chern.
I>. T.. Biochew~.
C.. Kamiyama,
T..
3. 339
Bi0phy.c. Salel,
Re.5.
A.. and