Concentrations of Tumor Necrosis Factor α and Progesterone within the Bovine Corpus Luteum Sampled by Continuous-Flow Microdialysis during Luteolysis in Vivo

Corpora lutea (CL) of mature, nonlactating Holstein cows (n = 12) each received surgical implants of a microdialysis system between Days 12 and 16 of an estrous cycle (estrus = Day 0). Fractions from dialyzed CL were collected every 30 min for 12 h each day for 7-9 days after surgery. Concurrent sampling of jugular venous blood allowed comparison between luteal dialysate and peripheral serum hormone concentrations. Six cows received no treatment, while 4 cows received prostaglandin F2 alpha (PGF; 25 mg, i.m.) and 2 cows received hCG (5000 IU, i.m.) within 48 h after surgery. Serum progesterone (P4) declined to < 1 ng/ml by Day 20 +/- 0.5 in 4 of 6 nontreated cows and by Day 15 +/- 0.6 in all 4 PGF-treated cows. Both of the hCG-treated cows had increased serum and dialysate P4 after treatment and did not show evidence of luteolysis by the end of their sampling period (Days 22 and 18), and 2 of 6 nontreated cows did not show evidence of luteolysis by the end of their sampling period (Days 22 and 24). All 8 cows undergoing spontaneous or induced luteolysis showed a significant rise (p < 0.01) in dialysate (but not serum) tumor necrosis factor alpha (TNF) after P4 began to decline. From the start of the decline in dialysate P4, intervals to first detectable TNF and to peak TNF, and duration of TNF in the dialysate were 25.8 +/- 8 h, 38.3 +/- 8 h, and 42.3 +/- 7 h, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)