Effect of gossypol on bull spermatozoa in vitro

In vitro effect of gossypol acetate on yellow perch (Perca flavescens) spermatozoa

Gossypol, a known antispermatogenic agent from the cotton plant genus Gossypium, was found to inhibit yellow perch sperm motility in vitro and lactate dehydrogenase activity in spermatozoa when used in a dose-dependent manner. This toxin also significantly decreased sperm fertilizing ability. Exposure of sperm suspension to a 200-µM concentration of gossypol caused sperm immobilization and a consequent lack of fertilization. Effects of gossypol on sperm motility and fertilizing ability were partially reversible when sperm suspensions were transferred to solutions without gossypol. This reversibility was proportional to the gossypol concentration. We observed a significant increase of abnormal embryos produced by the fertilization of spermatozoa pretreated with gossypol. This implies that gossypol could affect the sperm genome. The results indicate a usefulness for yellow perch sperm in studies of gossypol action mechanisms. Results of in vitro experiments suggest a potential for reproductive impairment in fish when using cottonseed-containing diets or organic fertilizers in yellow perch aquaculture. However, these observations should be confirmed in in vivo experiments with yellow perch and other species.

Characterization of gossypol-induced sperm abnormalities in bulls

To characterize sperm abnormalities induced by gossypol in cattle, young Brahman bulls (n=8) received either cottonseed meal delivering 8.2 g free gossypol/bull/d (treatment, n=4) or isonitrogenous soybean meal (control, n=4) for 11 wk. At slaughter, semen was collected from the following extragonadal sites: mediastinum/rete testis (Site 1), caput (Site 2), corpus (Site 3) and cauda epididymis (Site 4), and ductus deferens (Site 5). At least 200 fixed spermatozoa per site were examined via differential-interference-phase contrast (DIC) microscopy, with electron microscopy (EM) being employed with select samples. Sperm midpiece abnormalities were categorized as aplastic, fragile or asymmetric, with detached sperm heads being tabulated separately. Of these, aplastic defects were considered most likely to occur during spermatogenesis. Bull sperm midpiece lesions induced by gossypol were ultrastructurally similar to those observed in other, nonruminant, species. Combined midpiece abnormalities generally increased with extragonadal passage (EGP) in the treated bulls, as did fragile and asymmetric but not aplastic midpieces, or detached sperm heads. This pattern of EGP changes in bull sperm morphology following gossypol spermatoxicity suggests that structural weakness induced during spermatogenesis leads to secondary spermatozoal changes during EGP, possibly due to the imposition of motility stressors upon prior weakened structures.

Inhibition of sialyl transferase activity by gossypol acetic acid in human seminal plasma

Seventeen aliquots of 15 microliters seminal plasma of human origin were incubated with 25 micrograms, 15 micrograms, 5 micrograms and 2.5 micrograms gossypol acetic acid (GAA), dissolved in BWW containing 0.9% sodium chloride and 0.9% benzyl alcohol, at 37 degrees C for 60 minutes. Following incubation, activity of sialyl transferase (S.T.) was determined by a procedure involving incorporation of radioactive sialic acid into asialofetuin. The activity of S.T., expressed as cpm per hour per 15 microliters seminal plasma was compared to controls consisting in incubation of sperm in BWW containing 0.9% benzyl alcohol and 0.9% sodium chloride. The activity of S.T. in controls represented 61.3 +/- 8.0%-67.7 +/- 8.9% of the activity obtained by incubation with BWW only. GAA was found to exert a dose-dependent inhibition of S.T. activity, ranging from 38.3 +/- 20.6% to 53.4 +/- 19.4% (with 25 micrograms) and from 11.3 +/- 14.8% to 21.9 +/- 14.8% (with 2.5 micrograms).

Inhibition kinetics of NAD-linked enzymes by gossypol acetic acid

Effects of gossypol on human spermatozoal enzymes were investigated. This compound was found to be a potent inhibitor of the NAD-linked enzymes, glucelaldehyde-3-phosphate dehydrogenase (GA3PDH), lactate dehydrogenase (LDH), malate dehydrogenase (MDH), and isocitrate dehydrogenase (ICDH). MDH was inhibited by gossypol when the reaction was carried out in malate-oxalacetate (direct) or oxalacetate-malate (reverse) directions. The I50 of gossypol for the direct reaction was 2.9 microM, whereas that for the reverse reaction was 1.2 microM. Reciprocal plots due to Lineweaver-Burk showed that MDH is inhibited in a noncompetitive manner with respect to both reactions. LDH was also inhibited by this compound when pyruvate or alpha-ketobutyrate was used as a substrate. Gossypol was a noncompetitive inhibitor for LDH. The I50 of gossypol for LDH were 9.8 microM and 11.3 microM, when using pyruvate and alpha-ketobutyrate, respectively as substrates. The I50 of gossypol for GA3PDH and ICDH were 110 microM and 2.7 microM, respectively.

Metabolism of round spermatids in the rat: effect of gossypol on the glucose transport

Low dose of gossypol (5 microM) completely inhibited uptake of 2-deoxy-D-glucose by rat spermatids. With gossypol 2-deoxy-D-glucose transport into spermatids increased curvelinearly for 10 minutes after the start of incubation, but reached a plateau afterwards, whereas without gossypol it continuously increased. The levels of fructose-1,6-bis-phosphate (FBP) and ATP were inversely correlated when the cells were exposed to glucose. However, in the presence of gossypol the levels of ATP and FBP decreased simultaneously. In addition, gossypol at 10 microM stimulated oxygen consumption when lactate was present. These results suggest that gossypol probably inhibits glucose transport into spermatids by lowering the ATP level by uncoupling respiratory chain-linked phosphorylation.