CONCENTRATIONS OF TUMOR-NECROSIS-FACTOR-ALPHA AND PROGESTERONE WITHIN THE BOVINE CORPUS-LUTEUM SAMPLED BY CONTINUOUS-FLOW MICRODIALYSIS DURING LUTEOLYSIS IN-VIVO

Corpora lutea (CL) of mature, nonlactating Holstein cows in = 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 F-2 alpha (PGF;25 mg, i.m.) and 2 cows received hCG (5000 IU, i.m.) within 48 h after surgery. Serum progesterone (P-4) 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 P-4 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 P-4 began to decline. From the start of the decline in dialysate P-4, 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. TNF was not detectable in the dialysate of cows prior to the onset of P-4 decline and was not detectable at any time in the dialysate of cows that did not undergo luteolysis during the sampling period. Dialysate P-4 values paralleled serum values, but serum TNF did not fluctuate and was not correlated with day of the cycle or with dialysate TNF. To our knowledge, this is the first report of microdialyzed bovine CL in vivo, and we find the technique capable of providing novel profiles of intraluteal hormone dynamics. We conclude that a discrete rise in intraluteal TNF is temporally related to luteolysis in the cow and that the onset and peak activity of luteal TNF occurs after P-4 begins to decline.