Validation of radioimmunoassays for two salmon gonadotropins (GTH I and GTH II) and their plasma concentrations throughout the reproductivecycle in male and female rainbow trout (Oncorhynchus mykiss).
RIAs were developed for the two salmon gonadotropins (GTH I and GTH II) and used to measure plasma GTH throughout the life of the rainbow trout, Oncorhynchus mykiss. The RIA for GTH II was specific and sensitive (< 0.001% cross-reaction with GTH I, mean sensitivity = 0.26 +/- 0.02 ng/ml). The RIA for GTH I was less specific and less sensitive than the GTH II RIA (9.7% cross-reaction with GTH II, mean sensitivity = 2.34 +/- 0.23 ng/ml). In both males and females, the levels of GTH II remained undetectable (< 0.3 ng/ml) throughout most of the reproductive cycle, until shortly preceding spermiation/ovulation, when they began to rise. Concentrations of plasma GTH II were maximal at spermiation/ovulation. In both sexes, plasma profiles of GTH I differed from those of GTH II. The plasma GTH I concentration in females was elevated during early vitellogenesis. It then fell to a basal level shortly before ovulation and finally was elevated again at ovulation. In males, increases in plasma GTH I were seen a year before spermiation and again later, during the final stages of testicular growth. These results support the contention that GTH I mediates gonadal growth, whereas GTH II regulates the final stages of maturation and ovulation/spermiation. In rainbow trout, plasma profiles of GTH I and GTH II mimic the cycles of plasma FSH and LH, respectively, in the ovulatory cycle of higher vertebrates.
Prat
F
F
Department of Biology and Biochemistry, Brunel University, Uxbridge, Middlesex, United Kingdom. francisco.prat@brunel.ac.uk
Sumpter
J P
JP
Tyler
C R
CR
D000818:Animals; D000918:Antibody Specificity; D005260:Female; D006065:Gonadotropins, Pituitary / Q000032:analysis* / Q000097:blood; D007457:Iodine Radioisotopes; D008297:Male; D017684:Oncorhynchus kisutch; D017686:Oncorhynchus mykiss / Q000378:metabolism*; D010060:Ovulation / Q000502:physiology; D011863:Radioimmunoassay; D012098:Reproduction / Q000502:physiology*; D012621:Seasons; D013045:Species Specificity; D013091:Spermatogenesis / Q000502:physiology
D006065:Gonadotropins, Pituitary; D007457:Iodine Radioisotopes; C057763:gonadotropin- pituitary, beta-subunit I, salmon