Calcium sensitivity and cardiac performance in genetic and renal models of hypertension.
We have compared cardiac performance, hypertrophy and sensitivity to calcium and verapamil of hearts of six to nine-month-old spontaneously hypertensive rats (SHR), two-kidney, one clip renal hypertensive rats (RHR) and age-matched controls. Cardiac output and heart rate were measured using an isolated perfused heart preparation. Mean blood pressure (BP) and heart weight were equally increased in SHR and RHR as was optimal left atrial filling pressure. Cardiac output was increased in both SHR and RHR at any given work load; this improvement was seen especially in SHR and at high aortic pressure (160 cm H2O) was significant in SHR but not RHR. In low [Ca2+], 0.6 mM, cardiac output of RHR and controls fell markedly, but changed little in SHR, whereas in high [Ca2+], 5.1 mM, cardiac performance deteriorated in SHR but was improved in RHR and controls. Verapamil 2 X 10(-7) M reduced Ca2+ responsiveness of RHR and controls threefold but had no effect in SHR. The results suggest there may be an abnormality of cardiac calcium utilization in inherited but not in acquired hypertension.
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D002118:Calcium / Q000494:pharmacology*; D002302:Cardiac Output / Q000187:drug effects*; D006321:Heart / Q000187:drug effects / Q000503:physiopathology*; D006973:Hypertension / Q000503:physiopathology*; D006978:Hypertension, Renovascular / Q000503:physiopathology*; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D014700:Verapamil / Q000494:pharmacology*
D014700:Verapamil; D002118:Calcium