Secretion and regulatory mechanism of leptin during pregnancy in the golden hamster (Mesocricetus auratus)
Secretion and regulatory mechanism of leptin during pregnancy in the golden hamster （Mesocricetus auratus）

The aim of this study is to investigate the secretion pattern and regulatory mechanism of leptin during pregnancy in the golden hamster (Mesocricetus auratus). 100 pregnant golden hamsters were separated into 16 groups and the serum was sampled daily throughout gestation for the leptin assay. Results indicated that a gestational leptin profile existed during pregnancy in the golden hamster. To investigate if endocrine conditions during pregnancy contribute to this gestational leptin profile, serums collected during different reproductive stages were added to the adipocyte culture medium. Results showed that sera collected from all reproductive stages have significant stimulating effect on the secretion of leptin as compared with the control (P < 0.05). Steroid extracted and non-extracted serums from day 2 of estrus cycle (cycling serum ) and day 2 of the lactation have the same effect on the secretion of leptin (P > 0.05). However, sera from mid and late pregnancy significantly stimulate leptin secretion as compared with the cycling sera (P < 0.01). Serum collected on day 15 of pregnancy have the strongest stimulating effect on leptin secretion compared with sera collected on day 8 (P < 0.0001) and day 12 (P < 0.001) of the pregnancy. But after the extraction of steroid hormones, sera collected during different reproductive stages have the same effect on leptin secretion in vitro. Further study showed that dexamethason, progesterone and insulin stimulated while estradiol suppressed leptin secretion in vitro. Our results suggested that steroid hormones (or other steroid factors) have significant regulating effect on the leptin secretion during pregnancy and they may be the most important contributors of the gestational leptin profile in the golden hamster.