Different behaviour of normotonous and spontaneously hypertensive rats with vitamin D intoxication

Spontaneously hypertensive rats (SHR) were found to tolerate the consequences of vitamin D intoxication much better than Wistar Kyoto rats (WKY). This is obvious from the 10-fold higher death rate of WKY rats and from the considerable differences of the tissue reactions occurring in the aorta, the cardiac muscle and the arterial vessels between WKY rats and SHR. Thus, myocardial alterations are much rarer in SHR; this holds also for the aorta calcification which is less pronounced in SHR and which is age-dependent in so far as it is almost absent from one year onward. Giant granulomas as a result of vitamin D intoxication were found in juvenile SHR at a time where they would otherwise no yet have occurred at a frequency observed in old untreated SHR. Common to both WKY rats and SHR is the formation of vascular alterations (plasmatic vasculosis) which reveal--though less pronounced with SHR--the angiotoxic action of vitamin D. For these considerable differences in the behaviour of WKY and SHR in vitamin D intoxication the different Ca-binding and transport properties of the arterial plasma membranes should be responsible, which is likely to be due to a defect in the Ca-transport mechanism of the smooth vascular muscle. The importance of these findings for the use of vitamin D intoxication in arteriosclerosis research as well as for studies on the pathogenesis of permeability disorders and alterations of the arterial vascular system is pointed out.