Alterations in Calcium Transport and Binding by the Plasma Membrane of Mesenteric Arteries from Spontaneously Hypertensive Rats
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The effect of Sr++, Ba++ and Mn++ on calcium uptake by a plasma membrane-enriched fraction from mesenteric arteries of spontaneously hypertensive rats (SHR) was studied to determine what alterations in divalent cation interactions are associated with hypertension. 45Ca++ uptake in the presence of ATP by this fraction from SHR was significantly greater than that of normotensive rats (NWR). This 45Ca++ uptake by these fractions from both types of rat could be reduced by Ba++, Sr++ and nonradioactive Ca++, but not by Mn++; the ability of these cations to compete with 45Ca++ was in the following order Ca++ greater than Sr++ greater than Ba++. In contrast, 45Ca++ uptake in the absence of ATP by this subcellular fraction from SHR was significantly less than that of NWR, and this passive 45Ca++ binding could be displaced by Mn++ in addition to the other cations. Both qualitative and quantitative differences were found between SHR and NWR in this study of the effects of cations on calcium uptake by arterial plasma membrane. These results suggest that the plasma membrane of SHR arteries has calcium-binding and transport properties that are different from those of NWR. However, there is not a complete correlation between the reported effects of the cations on contraction of other arteries in hypertension and on calcium uptake by membranes of SHR and NWR.
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