Tissue Guanosine-3′,5′-Cyclic Monophosphate Levels and Soluble Guanylate Cyclase Activity

Abstract

A B S T R A C T The relationship between the subcellular distribution of guanylate cyclase and tissue guanosine-3',5'-cyclic monophosphate (cGMP) levels was investigated in rat testes after surgically induced unilateral cryptorchidism. Placement of one of a testis pair in the abdominal cavity results in loss of testicular weight and function in the abdominal testis whereas the remaining scrotal testis appears to be functionally normal. Within 5 days after surgery, tissue cGMP levels were increased by twofold in the abdominal testis. A fourfold elevation was noted from 10 to 30 days after surgery. Whereas the homogenate guanylate cyclase activity was only slightly elevated 10 and 20 days postoperatively, a 200% increase in the soluble guanylate cyclase activity was seen at 5 days. Between 10 and 30 days, the rise in activity was >250% (P < 0.01). An increase in soluble guanylate cyclase activity was noted when the data were expressed as per milligram protein, per milligram DNA or per whole testis. Conversely, particulate guanylate cyclase activity was reduced by 40% in the cryptorchid testis. Kinetic analysis of the soluble enzyme prepared from abdominal and scrotal testes yielded linear Lineweaver-Burke plots for both enzyme preparations with an identical Km for guanosine triphosphate, but a threefold higher maximal velocity for the abdominal enzyme. When the soluble guanylate cyclases from both testes were mixed and assayed together, the activities were additive rather than exhibiting synergism or inhibition. These experiments indicate that the

Ovarian cyclic GMP concentration and guanylate cyclase activity in immature rats after treatment with pregnant mare serum gonadotrophin

“…Correlation of tissue guanylate cyclase activity and cGMP concentrations has been reported by other workers; e.g. in cryptochid rat testis (Spruill et al 1978) and in rat kidney (Craven & DeRubertis, 1976). In our studies on rabbit ovaries (Patwardhan & Lanthier, 1984).…”

“…The cytosol and particulate enzymes are thought to be two different entities (Kimura & Murad, 1974;Chrisman, Garbers, Parks & Hardman, 1975) and can be regulated independently. Thus, experimentally in¬ duced cryptochidism caused an increase in the cytosol guanylate cyclase activity of rat testis while the par¬ ticulate activity was reduced (Spruill, Steiner & Earp, 1978). During liver regeneration, particulate activity was found to be increased and cytosol activity un¬ changed (Goridis & Reutter, 1975;Zelig & Goldberg, 1977) or decreased (Koide, Earp, Ong & Steiner, 1977).…”

Cyclic GMP phosphodiesterase and guanylate cyclase activities in rabbit ovaries and the effect of in-vivo stimulation with LH

“…The incubation conditions and the substrate concentration (1 mmol/1) used for measuring cyclase activity were similar to those of Kimura & Murad (1974) and Spruill, Steiner & Earp (1978). The values for guanylate cyclase activity found in the cytosol and particulate fractions of ovaries of control and LHtreated rabbits are shown in Table 2.…”

Compartmentalization of Cyclic Nucleotide-Mediated Hormone Action

“…Hormones and neurotransmittors undoubtedly affect the activity of the enzyme but do not do so directly. Early during testicular development all forms of guanylate cyclase activity are elevated when compared to adult levels, but the soluble activity remains elevated later into development (65). Several examples have been studied that involve the processes of growth, development, or.…”

“…It is logical to assume that in addition to the acute regulation of existing guanylate cyclase activity, mechanisms exist by which the total concentration of the different forms of guanylate cyclase are modulated. Testicular atrophy produced by uni lateral cryptorchidism produces a sustained elevation of the soluble activity (65). involution of a tissue.…”