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There are identified 3 proteins with molecular mass of 63, 73 and 132 kDa, exhibiting the properties of the hyaluronidase of the 1st type in the liver, spleen, renal papilla, skin and serum by the method of zymography. A protein with a molecular mass of 73 kDa was detected in all studied tissues and serum, while protein with a molecular mass of 63 kDa was present only in the tissues, and the protein with molecular mass of 132 kDa was present only in the serum. It is discussed the possibility of aggregation of 63 kDa protein molecules in the dimers with the formation of a 132 kDa protein in the serum.

Effects of desmopressin (arginine vasopressin V2 receptor agonist) were studied for elucidation of the possible role of the kidneys in the regulation of blood hyaluronidase activity. Similar to vasopressin, intraperitoneal administration of desmopressin to Wistar rats increased blood hyaluronidase activity by 30%. Against the background of water load, nether desmopressin nor vasopressin increased blood hyaluronidase activity. The possibility of renal secretion of hyaluronidase into the blood as a mechanism of antidiuretic activity of vasopressin and its role in the regulation of water metabolism are discussed.

Effect of dehydration and arginine vasopressin treatment (Arg-VP Sigma, USA, 50 ng/100 g b.wt. ip.) on the blood plasma hyaluronidase activity in Wistar rats was studied. It was found that the pH optimum of the enzyme activity was in the range of 3.5-3.7 that is characteristic for the hyaluronidase type 1. Water deprivation for 1 day was followed by significant increase in the blood plasma hyaluronidase activity. The same response was observed under vasopressin treatment. The possible role of increased plasma hyaluronidase activity in the regulation of water balance is discussed.

Specific vasopressin-sensitive phosphorylation of the collecting duct proteins with molecular mass 15, 20, 25, and 33 kDa, was revealed. The proteins implemented the hormonal effect of vasopressin by means of qualitative molecular modifications with subsequent phosphorylation.

Endogenous phosphorylation of proteins in cell suspensions of collecting tubes was studied. Using SDS disc electrophoresis in polyacrylamide gel with subsequent autoradiography, it was shown that vasopressin increases the 32P incorporation into two proteins with molecular masses of 15 kDa and 33 kDa, which serve as endogenous substrates for cAMP-dependent protein kinase. The hormone-dependent phosphorylation of these proteins was typical of the membrane fraction of collecting tube cells but was absent in the cytosolic fraction. The results obtained are suggestive of the direct involvement of vasopressin in the regulation of membrane protein phosphorylation by cAMP-dependent protein kinase which may increase the permeability of cells for H2O.

Using SDS-PAAG electrophoresis with subsequent autoradiography, several proteins from plasma membranes and cell cytosol of rat kidney papillary zone were identified as substrates for endogenous cAMP-dependent protein kinases. The cAMP-dependent phosphorylation of plasma membrane proteins was made possible only after the destruction of membrane vesicles. Plasma membrane and cytosol fractions were found to contain a 58 kDa protein whose properties are similar to those of the regulatory subunit of cAMP-dependent protein kinase of the second type. It was shown also that the content of endogenous substrates of cAMP-dependent protein kinases in cell cytosol is higher than that in plasma membranes.

The aldosterone, cAMP and ADH receptors were studied in kidneys of 10-14- and 60-day old rats. Concentrations of aldosterone and cAMP receptors were reduced, while ADH binding was increased during the period of maturation of kidney functions. The investigation of the affinity and molecular weights of cAMP and ADH receptors suggests their complex nature and altering of their individual properties during ontogenesis. Aldosterone and cAMP with their receptors seem to participate in the regulation of gene activity in ontogenesis and ADH seems to participate in the formation of its own receptors.