Direct effects of angiotensin I, angiotensin II, an ACE inhibitor and a serine proteinase inhibitor on cultured heart cells from spontaneously hypertensive rats.

Abstract

1. The purpose of the present study was to investigate how angiotensin I (AI), angiotensin II (AII), an angiotensin converting enzyme inhibitor (ACE inhibitor; ACE-I) and a serine proteinase inhibitor contribute to the protein metabolism of cultured newborn spontaneously hypertensive rats (SHR) heart cells. We examined the uptake of [3H]-uridine and [3H]-proline into cultured cardiac myocytes and fibroblasts, respectively. 2. Both AI and AII increased the uptake of [3H]-uridine into myocytes in a concentration-dependent manner. However, the effect of AI was denied in the presence of the ACE-I with the concentration of 10(-6) g/mL. Both AI and AII increased the uptake of [3H]-proline into cardiac fibroblasts in a concentration-dependent manner. However, this effect was only partially abolished in the presence of 10(-6) g/mL of the ACE-I, which was the maximal concentration that did not exert any effect on the [3H]-proline uptake. In the presence of AII receptor antagonist, [Sar1, Leu8]-AII, the uptake of [3H]-proline into cardiac fibroblasts was completely inhibited. Moreover, the stimulatory effects of AI on the uptake of [3H]-proline into cardiac fibroblasts were completely inhibited in the presence of a serine proteinase inhibitor in addition to the ACE-I. 3. These results suggest that an ACE-I has different effects on protein metabolism in the heart and also suggest the presence of serine proteinase in cultured cardiac fibroblasts from SHR.