[Effect of pH on Ca-binding properties of calmodulin and on its interaction with Ca-dependent phosphodiesterase of cyclic nucleotides].

The fluorescence of dansyl immobilized on bovine brain calmodulin is sensitive to Ca2+. This effect is due to Ca2+ attachment to specific Ca2+-binding sites of calmodulin and is maintained within a wide range of pH. The native and dansyl-modified calmodulin preparations exert similar activating effects on Ca-dependent phosphodiesterase of cyclic nucleotides and have practically the same affinity for the enzyme.

[Participation of adenylate cyclase in conducting hormonal signals through membranes].

Mechanisms are considered which conduct and amplify a hormonal signal with participation of adenylate cyclase. It is shown that cell sensitivity to hormone is governed by the constant of receptor affinity for hormone, by the content of receptors in the membrane as well as of the degree of receptors conjugation with the enzyme. Mechanisms regulating the amount of receptors in the membrane, the role of guanylic and other purine nucleotides in their functioning are discussed.

[Role of guanyl nucleotides in regulation of activity of heart adenylate cyclase by chloride ions].

Guanyl nucleotides enhance the activating effect of chloride ions on adenylate cyclase of rabbit heart sarcolemma. Chloride ions decrease the lag period in the effect of guanyl-5'-ylimidodiphosphate (Gpp(NH)p), the non-hydrolyzed analog of GTP, on adenylate cyclase. Guanyl nucleotides and chloride ions exert a synergistic effect on the enzyme activation.

[Reconstitution of sensitivity of solubilized rabbit heart adenylate cyclase to hormones and guanyl nucleotides].

Solubilization of adenylate cyclase by lubrol PX results in a loss of the enzyme sensitivity to hormones; however, the enzyme retains its ability to be activated by guanyl nucleotides and NaF. Lubrol WX devoids adenylate cyclase of its sensitivity to hormones and NaF. Solubilization causes a shift in the pH optimum of the enzyme towards neutral values of pH and significantly decreases the thermal stability of adenylate cyclase.

[Effects of GTP and NaF on rabbit heart adenylate cyclase activated by guanyl-5'-ilimidodiphosphate].

The GTP analog, guanyl-5'-ilimidodiphosphate (Gpp(NH)p) activates rabbit heart adenylate cyclase with the lag period eliminated by isoproterenol. The Gpp(NH)p-isoproterenol-induced state of adenylate cyclase is very stable and is retained after removal of the effector excess and a 40-min incubation at 37 degrees. GTP and NaF decrease the activity of Gpp (NH)p-stimulated adenylate cyclase.

[Cyclic 3,5-adenosine monophosphate content and calcium transport in the aorta in hypertension due to experimental renal insufficiency].

The calcium, magnesium, and cyclic AMP content and 45Ca transport in the aorta and iliac artery and the mechanical properties of these vessels were studied in rats with experimental renal insufficiency. The development of hypertension was attended by an increase in the magnesium content in the vascular wall, a certain decrease in the cyclic AMP level, marked disturbance of 45Ca transport, and changes in the mechanical properties of the vascular wall. The use of dihydrotachysterol or a complex of sex steroids which correct calcium metabolism led to a decrease of arterial hypertension.

[Two forms of cyclic nucleotide phosphodiesterase and Ca-dependent protein regulator from rabbit skeletal muscles].

In rabbit skeletal muscle extracts the activity of phosphodiesterase practically insensitive to the increase of Ca2+ concentration from 10(-8) M up to 10(-5) M. The Ca2+-dependent protein regulator is separated from phosphodiesterase at the stage of isolation and purification. The activity of phosphodiesterase devoid of the protein regulator is inhibited by Ca2+ (10(-5)--10(-3) M).

[Separation and investigation of the regulatory properties of two forms of cyclic nucleotide phosphodiesterase from rabbit heart--sensitive and insensitive to Ca-dependent regulator protein].

Two forms of cyclic nucleotide phosphodiesterase (ES 3.1.4.

[Isolation, purification and characterization of regulatory properties of adenylate cyclase from rabbit heart].

Rabbit heart membranes possessing the adenylate cyclase activity were isolated and purified by extraction with high ionic strength solutions and centrifugation in the sucrose density gradient. It was shown that the membranes are characterized by a high percentage of cholesterol (molar ratio cholesterol/phospholipids is 0.24) and an increased activity of Na, K-ATPase, which suggests the localization of adenylate cyclase in the sarcolemma.