Regional distribution of vascular resistance in two models of experimental renovascular hypertension.

The regional distribution of the peripheral vascular resistance was studied in normotensive and hypertensive Wistar rats. Two models of experimental hypertension were investigated: (I) in 32 animals the right renal artery was constricted by a silver clip (two-kidney Goldblatt hypertension); (II) in 46 animals the left kidney was removed and the right renal artery was clipped as in the first group (one-kidney Goldblatt hypertension). The normotensive control group comprised 61 untreated animals of the same strain and age. The distribution of cardiac output to 14 tissues was determined by means of the particle distribution technique. The resistance was increased in all regions investigated, a decreased or unchanged resistance was not observed. For most of the investigated tissues the regional resistance was increased exactly in proportion to the total peripheral resistance (TPR). Exceptions to this were found in 2 regions where the change of local resistance deviated from that of TPR: the splanchnic area and the skeletal muscle. In both cases the 2 models differed from each other. In the two-kidney model the increase of resistance in the splanchnic circulation was more intense than in other organs. In contrast, in the one-kidney model the local change of resistance was less than that of TPR. The change of skeletal muscle resistance was not significantly different from the change of TPR in the two-kidney model, while in the one-kidney model the increase of local resistance was significantly higher than that of TPR. It is concluded that the etiology of the abnormal resistance is different in the 2 models investigated and that known extrinsinc pressor factors may play a role in the two-kidney, but not in the one-kidney Goldblatt hypertension.