Heat Stress-Induced Alterations in the Synthesis and Secretion of Proteins and Prostaglandins by Cultured Bovine Conceptuses and Uterine Endometrium¹

Abstract

Effect of in vitro heat stress on protein and prostaglandin synthesis and secretion by bovine conceptuses and endometrium was examined. Conceptuses (n = 11) and endometrium (n = 10) obtained on Day 17 of pregnancy were cultured at thermoneutral (39°C, 24 h) or heat stress (39°C, 6 h; 43°C, 18 h) temperatures in medium supplemented with L-[4,5–³H]leucine (100 μCi) and arachidonic acid (10 μg/ml). Radiolabeled protein secreted into culture medium increased with time in both groups. Heat stress reduced (p<0.001) incorporation of [³H]leucine into intracellular and secreted proteins by conceptuses but did not alter incorporation of [³H]leucine by endometrium. In particular, heat stress reduced by 72% the secretion of bovine trophoblast protein-1, the conceptus polypeptide believed to cause extension of luteal lifespan. Two-dimensional, sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicated that heat stress altered the array of proteins in endometrial and conceptus tissues, as evidenced by the induction of “heat-shock proteins.” Endometrial secretion of prostaglandin F (p<0.001) and conceptus secretion of prostaglandin E₂ (p<0.05) increased in response to heat stress. Sensitivity of bovine conceptuses and endometrium to heat stress in vitro suggests that infertility associated with maternal heat stress may be caused, partially by alterations in signals required for maintenance of the corpus luteum during early pregnancy.

Author notes

¹

This study was supported in part by USDA Grants 84-CRSR-2–2419 and 85-CRSR-1–1871. This is Journal series No. 8740 of the Florida Agricultural Experimental Station.