Effects of leptin administration on development, vascularization and function of Corpus luteum in alpacas submitted to pre-ovulatory fasting

- This is the first in vivo report of the effect of the hormone leptin on the vascularization of the Corpus luteum.
- Leptin administration during pre-ovulatory fasting increased the vascularization of the C. luteum in alpacas.
- A positive correlation between CL vascularization, CL diameter and plasma progesterone was determined. These relationships highlight the need for further studies to get a better understanding of the role of leptin in luteal function in alpacas.

The objective of this study was to determine the effect of leptin administration on the development, vascularization and function of Corpus luteum (CL) in alpacas submitted to pre-ovulatory fasting. Fourteen alpacas were kept in fasting conditions for 72 h and received five doses of o-leptin (2 μg/kg e.v.; Leptin group) or saline (Control group) every 12 h. Ovulation was induced with a GnRH dose (Day 0). The ovaries were examined every other day by trans-rectal ultrasonography (7.5 MHz; mode B and power Doppler) from Day 0 to 13 to determine the pre-ovulatory follicle diameter and ovulation, and then to monitor CL diameter and vascularization until the regression phase. Serial blood samples were taken after GnRH treatment to determine plasma LH concentration; and every other day from Days 1 to 13 to determine plasma progesterone and leptin concentrations. The pre-ovulatory follicle and CL diameter, LH, progesterone and leptin plasma concentrations were not affected by treatment (P > 0.05). The vascularization area of the CL was, nevertheless, affected by the treatment (P < 0.01) with significant differences between groups at Days 3, 7 and 9 (P < 0.05). The Leptin group had a larger maximum vascularization area (0.67 ± 0.1 compared with 0.35 ± 0.1 cm2; P < 0.05). In addition, there was a positive correlation between CL vascularization, CL diameter and plasma progesterone. The exogenous administration of leptin during pre-ovulatory fasting increased the vascularization of the CL in alpacas in vivo.