Responses to calcium of chemically skinned vascular smooth muscle from spontaneously hypertensive rats.

The contractile responses to Ca2+ of chemically skinned vascular smooth muscle from spontaneously hypertensive rats (SHR) and an inbred strain of Dahl salt-resistant rats (R/JR) were compared. In the absence of added calmodulin, skinned tail artery of these two strains responded similarly to Ca2+ in the concentration range of 8.5 X 10(-8) M to 6.6 X 10(-6) M Ca2+. Calmodulin (0.12 microM) decreased the ED50 for Ca2+ and increased the contractile response similarly in both strains. There is a known genetic locus regulating vascular reactivity and blood pressure which is polymorphic between these two particular strains. The present results suggest that this genetic difference is more likely to reside in the smooth muscle cell membrane than in the contractile apparatus.