Hypertensive factor in different models of experimental hypertension.

A hypertensive factor (HF), isolated from rat erythrocytes, has been shown to stimulate in vitro calcium uptake in aortic rings and to elevate blood pressure when injected into normotensive rats. In the present study, we investigated tissue responsiveness to HF in spontaneously hypertensive rats (SHR), Wistar Kyoto rats (WKY), 2-kidney, 1-clip renovascular hypertensive rats and uninephrectomized rats that were given water or saline to drink or that were treated with DOCA and given water or saline to drink (DOCA-salt). Tissue responsiveness was determined by incubating aortic rings from the rats in the different groups with a constant amount of HF and measuring "lanthanum-resistant" calcium uptake. Tissue sensitivity to HF was greater in SHR than in WKY. In contrast, tissue sensitivity to HF was not enhanced in 2-kidney, 1-clip renovascular and DOCA-salt hypertensive rats relative to their appropriate controls. These results suggest that the increased tissue responsiveness to HF found in SHR is not universally associated with elevated blood pressure; increased tissue sensitivity seems to be a specific characteristic of genetic hypertension.