EFFECT OF TREATMENT WITH VITAMIN-D3 ON THE RESPONSES OF THE DUODENUM OF SPONTANEOUSLY HYPERTENSIVE RATS TO BRADYKININ AND TO POTASSIUM

1 The diet of spontaneously hypertensive rats (SHR) and normotensive W istar-Kyoto (WKY) and Wistar (NWR) rats was supplemented with either 2 % calcium lactate in the drinking water or 12.5-mu-g vitamin D3 100 g- 1 body weight daily by gavage, for 14 days. 2 The blood pressure of th e SHR treated with either calcium or vitamin D decreased to the same l evels as that of WKY and NWR. 3 The response to bradykinin of the SHR isolated duodenum, which is predominantly contractile, upon treatment with vitamin D (but not with calcium), became predominantly relaxant, approaching the normal behaviour of the WKY and NWR duodenum. 4 The re laxant responses of the SHR and WKY duodenum to potassium were smaller than those of NWR, but treatment with vitamin D increased the respons e in all three rat strains. 5 It is concluded that, besides sharing th e hypotensive effect of calcium, vitamin D treatment of SHR has an eff ect on the duodenum smooth muscle which might be due to calmodulin-dep endent activation of calcium-dependent potassium channels.