Seasonal variation in plasma and corpus luteum oestradiol-17B and progesterone concentrations of the lizard Cordylus p. polyzonus (Sauria: Cordylidae)
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Seasonal variation in plasma and corpus luteum oestradiol-17B and progesterone concentrations of the viviparous lizard Cordylus p. potyzonus is described. Steroid concentrations were measured by radioimmunoassay. Plasma oestradiol-17B concentration increased from basal values in late autumn (May) and peaked in mid-spring (October), during which time females were vitellogenic. Plasma oestradiol-17B concentration declined to basal values in the late spring (November) when female ovulate, remaining low until the onset of tne next vitellofenic phase in autum. Plasma progesterone concentrations of previtellogenic and early vitellogenic females (April-July) were basal, but increased during the later stages of vitellogenesis (August-October). Following ovulation in November, plasma progesteronec oncentrations were high throughout pregnancy, declining to basal values in April when parturition occurred. Oestradiol-17B was detectable in freshly formed corpora lutea (corpora haemorargica) during the first month of pregnancy (November), but declined to undetectable values thereafter. Corpus luteum progesterone concentratlon gradually increased as pregnancy proceeded, reaching a peak two months before birth, but declined thereafter. Progesterone concentration of postpartum degenerating corpora lutea (corpora albicantia) was considerably lower than that of corpora lutea during gestation.