A comparison of Ca++ incorporation in microsomal fractions from bovine, canine and rabbit aortic smooth muscle.

A comparative study was made of high and low affinity Ca++ uptake (ATP present) and binding (ATP absent) in microsomal fractions prepared by the same method from bovine, canine and rabbit aortic smooth muscle. Rabbit aortic microsomes incorporated slightly more Ca++ under control conditions than did the bovine or canine preparations. The effects of Sr++ (3.0 mM), neomycin sulfate (1.4 mM) and sodium nitroprusside (1.0 mM) on Ca++ incorporation in aortic microsomes from the three species were qualitatively and quantitatively similar. Sr++ inhibits primarily high affinity Ca++ uptake and binding; neomycin inhibits high and low affinity Ca++ binding and nitroprusside inhibits high affinity Ca++ uptake. Addition of oxalate potentiated high affinity Ca++ uptake in aortic microsomes from all three species. Thus, correlations between studies of effects of agents on Ca++ and tension in aortic strips of one of these species and on Ca++ uptake and binding by an aortic microsomal fraction of one of the other two species examined in this study would appear to be based upon qualitatively appropriate similarities.