[Phosphodiesterase characteristics of the fat cells in spontaneous hypertension in rats].

The activity of cAMP and cGMP phosphodiesterases in the cytosol and endoplasmic reticulum fraction of rat adipocytes was studied in animals of 4 groups: intact and adrenalectomized rats with normal pressure, intact and adrenalectmized rats with spontaneous genetic hypertension. It is shown that in animals of all groups the rate of cGMP hydrolysis in these fractions is higher than the rate of cAMP hydrolysis and that 90% of the activity of the enzymes that were studied occurs in the cytosol. Determination of the dependence of phosphodiesterase activity of cyclic nucleoides on a substrate concentration of 10(-8) to 10(-4) M made it possible to estimate the values of Hill's coefficients characterizing the degree of co-operation of the noted reactions. Increased activity of cAMP phosphodiesterase with low and high Km value and increased activity of cGMP enzyme were revealed in the cytosol of fat cells in rats with normal pressure after removal of the adrenals; the activity of these enzymes in the endoplasmic reticulum fraction did not change after adrenalectomy. In rats with spontaneous genetic hypertension the activity of both forms of cAMP and cGMP enzymes in the adipocyte cytosol increased after removal of the adrenals; in the microsome fraction the activity of cAMP phosphodiesterase with low Km value was reduced whereas the activity of cAMP phosphodiesterase with high Km value and the activity of cGMP in the region of high substrate concentration were increased.