Influence of testosterone on polyunsaturated fatty acid biosynthesis in Sertoli cells in culture.

Sertoli cells play a central role in spermatogenesis, its development and regulation. They are target cells for androgen action in the seminiferous tubules. The Sertoli cell is considered to be the most important cell type in the testis with regard to essential fatty acid metabolism. We studied the response to testosterone of cultured Sertoli cells from immature rats by determining the fatty acid composition of total cellular lipids as well as by the biosynthesis of polyunsaturated fatty acids. Fatty acid methyl esters were analysed by gas liquid chromatography and radiochromatography. Two doses of testosterone were tested (150 and 300 ng ml(-1)). Significant differences were found in fatty acids derived from total cellular lipids after 8 days in culture in the presence of testosterone (300 ng ml(-1), for 48 h). Compared to controls, the hormone produced a significant increase of 16:1 and 18:1 n-9, and of 18:2 n-6, and a decrease of 20:4 and 22:5 n-6 in total cellular lipids. The decrease in the n-6 fatty acid ratios 20:4/20:3, 20:4/18:2 and 24:5/24:4, and the increase in 18:1n-9/18:0 and 16:1n-9/16:0 ratios were taken as an indirect signal of testosterone effects on Delta5, Delta6 and Delta9 desaturase activities. The drop in Delta5 and Delta6 desaturase activities was corroborated by analysing the transformation of [1-14C]20:3 n-6 into its higher homologues. We concluded that testosterone modifies the fatty acid pattern of cultured Sertoli cells, and this hormone is involved in polyunsaturated fatty acid biosynthesis, modulating Delta5 and Delta6 desaturases activity.

Lipid dismetabolism in Leydig and Sertoli cells isolated from streptozotocin-diabetic rats.

This work evaluates how the abnormalities in fatty acid biosynthesis, already described in diabetic rats, were extended to Sertoli and Leydig cells isolated from testes of streptozotocin-treated rats. Both kinds of cells were incubated in the presence of labeled eicosa-8,11,14-trienoic acid. The uptake of the substrate and its conversion to arachidonic acid were significantly depressed in both cell types compared to the non-diabetic controls. The indirect evidence of this inhibition was observed in the total fatty acid pattern of the cells where the 20:4 n-6/18:2 n-6 ratio was significantly decreased. The addition of insulin to the incubation medium produced no changes in the uptake of the substrate by the cells. Under similar experimental conditions the synthesis of arachidonic acid was partially recovered, however, the values obtained were still below those ones of cells isolated from control animals. These results were correlated with the fatty acid profile of different lipid fractions of plasma and with the activity of enzymes involved in polyunsaturated fatty acids biosynthesis measured in the testicular microsomes of diabetic rats. We conclude that Sertoli and Leydig cells evidenced similar lipid disorders than those observed in the whole testis or in other tissues of diabetic rats, and that the biosynthesis of arachidonic acid is under insulin regulation.

Spontaneously hypertensive rats: eicosa-8,11,14-trienoic acid metabolism and arachidonic acid biosynthesis.

Delta 9, delta 6 and delta 5 desaturation activity and the thioesterification of eicosa-8,11,14-trienoic acid (DGLA) were measured in spontaneously hypertensive rats (SHR) compared to normotensive controls (WKY). SHR exhibited lower levels in the long-chain fatty acyl-CoA (LCFA) synthetase and in delta 6 and delta 5 desaturase activities in liver. The enzymatic activity changes were reflected on the fatty acid composition of liver microsomes. In testis, the thioesterification of DGLA and its conversion to arachidonic acid, (AA), at the delta 5 desaturation step were also depressed in SHR. We conclude that, in SHR, the alteration in polyunsaturated fatty acid (PUFA) metabolism may influence the synthesis of AA-derived eicosanoids involved in the control of blood pressure regulation.

Long-chain acyl-CoA synthetase of rat testis microsomes. Substrate specificity and hormonal regulation.

We investigated long-chain fatty-acyl-CoA synthetase activity in rat testicular microsomes. The apparent Michaelis constants (Km's) for the substrate fatty acids increased while their corresponding maximal velocities decreased in the order 18:3(n-3), 20:3(n-6), and 18:0. The reaction with 20:3 as substrate was diminished in the presence of a constant amount of either 18:0, 18:2(n-6), or 18:3(n-3) in a manner consistent with their action as simple competitive inhibitors, with the Ki values for 18:0 and 18:3(n-3) being of the same order of magnitude as their respective Km's. Adrenocorticotrophin and/or dexamethasone administration to intact rats caused a significant decrease in the thioesterification of all three substrates without producing any alteration in the fatty-acid composition of the microsomal membranes. These results indicate the presence of a broad-specificity activating enzyme in testis whose function is subject to hormonal regulation.

Arachidonic acid biosynthesis in non-stimulated and adrenocorticotropin-stimulated Sertoli and Leydig cells.

The biosynthesis of arachidonic acid in Sertoli and Leydig cells isolated from the testes of mature rats has been investigated. Both types of cells incorporated [2-14C]eicosatrienoic acid from the incubation medium and transformed it into arachidonic acid. The administration of adrenocorticotropin (ACTH) to the rats decreased the delta 5 desaturating activity in the isolated testicular cells, while ACTH produced no changes in the uptake of the substrate. Similar results were obtained when ACTH was added to the incubation medium of cells isolated from non-hormone treated rats. The total fatty acid composition of the Sertoli cells isolated from ACTH-treated rats showed a significant increase in the relative percentage of 18:2n-6 and a decrease in the C20 and C22 polyenes. This may indicate that ACTH exerts an inhibitory effect on delta 6, delta 5 and delta 4 desaturase activities. Addition of corticosterone to the incubation medium also produced a significant decrease in arachidonic acid biosynthesis. Because ACTH is known to stimulate the release of corticosterone in vivo, both hormones may act cumulatively in the regulation of arachidonic acid metabolism in Sertoli and Leydig cells.