Effects of l-Arginine in Rat Adrenal Cells: Involvement of Nitric Oxide Synthase*

Abstract

The effects of L-arginine on corticosterone production, cGMP, and nitrite levels were examined in zona fasciculata adrenal cells. L-Arginine significantly decreased both basal and ACTH-stimulated corticosterone production. This effect was still evident when steroidogenesis was induced by 8-bromo-cAMP and 22(R)-hydroxycholesterol, but not in the presence of exogenously added pregnenolone. L-Arginine increased cGMP and nitrite levels,; these effects were blocked by the nitric oxide synthase inhibitor, N(G)-nitro-L-arginine methyl-ester. Transport of L-[3H]arginine was rapid, saturable, and monophasic, with an apparent Km of 163+/-14 microM and a maximum velocity of 53+/-6 pmol/min x 10(5) cells. The basic amino acids L-lysine and L-ornithine, but not D-arginine or the nitric oxide synthase inhibitors N(G)-nitro-L-arginine methyl-ester and N(G)-nitro-L-arginine, impaired L-arginine uptake. Taken together, these results suggest that steroidogenesis in zona fasciculata adrenal cells may be negatively modulated by L-arginine-derived nitric oxide.

Characterization ofl-arginine transport in adrenal cells: effect of ACTH

“…Results obtained in transstimulation experiments indicate that both y ϩ and y ϩ -LAT systems are involved in L-arginine efflux, suggesting that both systems cooperate for L-arginine transport in Y1 cells. Our results also support the involvement of the y ϩ -LAT-2 carrier, in addition to the previously demonstrated y ϩ system, in L-arginine transport in rat adrenal ZF (6). The coexistence of several CATs of high and low affinity in the same cell type has been previously demonstrated in human placental microvascular endothelial cells (13), INF-␥-stimulated human monocytes (29), human platelets (33a), and a rat thyroid cell line (37).…”

“…Several lines of evidence support the inclusion of NO among the autocrine/paracrine regulators of adrenal function, as was also demonstrated for other endocrine tissues (9,11,18,26,35). In previous reports (6,7) we have demonstrated that NO donors inhibit steroid synthesis in adrenal cells. Moreover, we also reported that adrenal steroidogenesis is negatively modulated by an endogenous NO synthase (NOS) activity.…”

“…Nitrite levels were determined in cell-free medium at the end of the culture periods by a spectrophotometric assay that was based on the Griess reaction, as described previously (6). The nitrite contents given in RESULTS were expressed as nanomoles of nitrite per milligram of protein.…”

“…Because incubation of adrenal cells in the presence of L-arginine resulted in a significant inhibition of steroid production and a concomitant increase in nitrite plus nitrate and cGMP levels (6,8), we hypothesized that the endogenous production of NO could depend on extracellular L-arginine levels, and therefore, the activity of the L-arginine transport system could modulate NO production in adrenal cells.…”

Down-regulation of adrenal neuronal nitric oxide synthase mRNAs and proteins after deoxycorticosterone acetate-salt treatment in rats

“…This may be of pathophysiologic importance, since nNOS mRNA expression level in the decapsular portion of the adrenal gland of SHR were lower than in an age-matched Wistar-Kyoto rats (WKY) and the nNOS expression in the decapsular portion of the adrenal gland was modulated by pharmacological antihypertensive treatment [7]. Besides, NO can regulate the rate of aldosterone and corticosterone production in adrenal glomerulosa [10] and fasciculata [12,13,27] cells. In addition to the modulation of NO on adrenocorticomedullary functions, NO is found to be capable to regulate adrenal blood flow [28].…”