|Carroll, Jeffery - Jeff Carroll|
Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 7/24/2001
Publication Date: N/A
Technical Abstract: We previously reported that C-section (C-sect) pigs have greater basal and CRH-induced cortisol (CS) compared to natural birth (NB) pigs. This study evaluated StAR protein and cytochrome P450 side-chain cleavage enzyme (P450) protein expression in C-sect pigs compared to NB pigs. Eight sows were selected for the study (n=4 NB and n=4 C-sect). Gestation length did not differ between NB and C-sect pigs (113.6+/.1 and 113.2+/.3 d, respectively). Blood and tissue samples from 38 pigs were collected at birth. Remaining pigs were sustained with NB sows until 2 wk of age (n=39) at which time serial blood samples were collected following adminstration of porcine CRH (10 ug/kg) or saline. RNA was isolated from the pituitary and adrenal glands to evaluate mRNAs specific for pro-opiomelanocortin (POMC) and for the ACTH receptor. Adrenal samples were used in Western blots to determine StAR and P450 protein content. While basal serum CS was not different at birth (P=.86), adrenal expression of StAR protein was lower (P<0.0001) in C-sect pigs as compared to NB pigs. Interestingly, serum ACTH (P=0.0008) and ACTH receptor mRNA (P<0.06) were greater in C-sect pigs, suggesting a compensational effect due to the reduced expression of StAR protein. A developmental decrease was observed in serum CS (P<0.0001) and ACTH (P<0.044), while a developmental increase was observed in POMC mRNA (P<0.0001). ACTH receptor mRNA expression tended (P<0.07) to decrease with age. Both, serum CS and StAR protein expression were increased following the CRH challenge (P<.05) whereas no change was detected in P450 protein expression. Results suggest an important role for StAR and P450 adrenal proteins in mediating developmental- and hormonal-induced changes in CS synthesis and secretion in the young pig.