[Guanylate cyclase activity of the rabbit myocardium in normal conditions and in allergic states]

Activity of guanylate cyclase, regulation of the enzyme by means of hormones and other biologically active substances as well as level of cGMP were studied in rabbit myocardium of control animals and in animals with allergic impairment of the tissue. The enzyme was shown to exhibit no sensitivity to acetylcholine and histamine, which appears to occur as a result of the hormone-unspecific desensitization of the corresponding receptors in allergic impairment. Decreased basal activity of guanylate cyclase was accompanied by an increase in content of cGMP in myocardial tissue. This phenomenon was apparently also due to a decrease in phosphodiesterase activity, which is observed under the conditions of this pathology. At the same time, the decrease in the basal activity of guanylate cyclase was caused by impairment in active restoration of the enzyme in the allergic tissue. A decrease in the enzyme activation by means of azide and nitroprusside appears to be due to loss of hem, prosthetic group of the cyclase. Physiological functions of guanylate cyclase are discussed.