Ovary

Luteogenesis in Cyclic Ewes: Echotextural, Histological, and Functional Correlates

Abstract

To date it has not been possible to detect CL by ultrasonography, immediately following ovulation, in the ewe. Early CL detection is essential to be able to relate luteal outcome to the developmental pattern of the ovulated follicle and to confirm ovulation. Image analysis of the CL may be useful in providing a non-invasive picture of CL differentiation and function. This study was designed to use high resolution ultrasonography to monitor, and to correlate the echotextural, histological and functional attributes of the developing ovine CL from d 1 to 3 after ovulation. Ten ewes underwent twice daily transrectal ultrasonography and blood sampling from the day of synchronized estrus. Ewes were ovariectomized at 12-24, 36-48 and 60-72 h after ovulation. Ovaries collected were scanned in a water bath before processing them for histology. Ultrasonographic images of CL were analyzed for echotexture. Histological sections were analyzed for the percentage area of the CL occupied by blood clot or luteal tissue. Serum samples were analyzed for progesterone concentration. Numerical pixel value, heterogeneity and the percentage of the CL occupied by blood clot declined (P < 0.05) from 12-24 to 60-72 h after ovulation. Luteal area and serum progesterone concentration increased (P < 0.05) from 12-24 to 60-72 h. The results indicated that it was possible to visualize developing CL as early as 12-24 h after ovulation in the ewe. Echotexture of the CL was closely associated with its morphological and functional characteristics; image analysis holds promise for the non invasive monitoring of CL differentiation and growth.