| pubmed-article:8015320 | pubmed:abstractText | Mesenteric lymph vessels exhibit spontaneous contractions that are critical in lymph fluid propulsion. We hypothesized that endothelium-derived relaxing factor (EDRF), recently identified as being released by lymph vessels, regulates contractile activity in mesenteric lymph vessels. Porcine mesenteric lymph vessel rings in vitro were administered either prostaglandin F2 alpha (PGF2 alpha; 10(-6) M), which increases contractile activity, NG-monomethyl-L-arginine (L-NMMA; 10(-4) M), which blocks EDRF production, or PGF2 alpha + L-NMMA, while paired control vessel rings remained in Krebs buffer alone. Vessel segments stimulated with PGF2 alpha exhibited repetitive contractions with more regular rhythm and uniform morphology than control segments and significantly greater frequency, amplitude, and trough and active tensions. Inhibition of EDRF production significantly enhanced the frequency (3.9 +/- 0.5 vs 2.1 +/- 0.4 min-1) and amplitude (555 +/- 42 vs 378 +/- 62 mg) of basal spontaneous contractions compared to controls and appeared to elicit more uniform contractions with respect to rhythm and morphology. PGF2 alpha-stimulated vessels pretreated with L-NMMA demonstrated uniform contractions with significant increases in contraction frequency (6.3 +/- 0.7 vs 2.4 vs 0.9 min-1), amplitude (846 +/- 120 vs 495 +/- 99 mg), trough tension (738 +/- 146 vs -6 +/- 32 mg), and active tension (1584 +/- 192 vs 489 +/- 111 mg) compared to controls (P < 0.05 for each). The effects of L-NMMA on unstimulated vessels were reversed by the addition of L-arginine but not by D-arginine (10(-4) M for each).(ABSTRACT TRUNCATED AT 250 WORDS) | lld:pubmed |
