title: Intraluteal administration of a nitric oxide synthase blocker stimulates progesterone and oxytocin secretion and prolongs the life span of the bovine corpus luteum.
abstract: To test the role of nitric oxide (NO) in secretory functions of bovine corpora lutea (CL), two groups of four Holstein heifers each were treated as follows: Group 1, Nomega-Nitro-L-Arginine Methyl Ester (L-NAME), an inhibitor of nitric oxide synthase (NOS), on Day 11 or 12 of the cycle and Group 2, L-NAME on Days 17 and 18 of the cycle. All treatments were administered by an intraluteal microdialysis system (MDS). Drugs were infused for 4-hr periods on the designated days, and the treatment periods were preceded and followed by 4-hr control periods. Perfusate and jugular blood samples were collected at half-hour intervals. Perfusate samples were analyzed for progesterone (P4), oxytocin (OT), prostaglandin F2alpha (PGF2alpha), and leukotriene C4 (LTC4); jugular plasma samples were analyzed for P4, OT, and LH. Perfusion of L-NAME on Day 11 or 12 consistently increased P4 concentration in the perfusate, but had no effect on the life span of the CL. Perfusion of L-NAME on Days 17-18 also elevated P4 levels in the perfusate, and in addition, maintained P4 levels in the plasma of three of the four treated animals through Day 25 of the cycle. L-NAME perfusion also increased OT release concomitant with P4 into the perfusate at both the mid- and late-luteal phase treatments. For the most part, concentrations of LH, OT, and P4 in the jugular plasma samples collected during the perfusions were unaffected by treatments. L-NAME perfusion caused small, but significant (P < 0.05) increases in perfusate PGF2alpha and LTC4 at Days 17 and 18 and in LTC4 on Day 11 or 12. These data indicate that NO plays a direct luteolytic role in regression of the bovine CL.
authors.affiliation: Pennington Biomedical Research Center, Louisiana State University, Baton Rouge, Louisiana 70803, USA.
authors.forename: J J
authors.initials: JJ
authors.lastname: Jaroszewski
authors.forename: W
authors.initials: W
authors.lastname: Hansel
mesh_terms: D000818:Animals; D002417:Cattle; D003338:Corpus Luteum / Q000187:drug effects* / Q000378:metabolism; D015237:Dinoprost / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D004971:Estrus / Q000378:metabolism; D005260:Female; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors*; D010121:Oxytocin / Q000378:metabolism*; D011374:Progesterone / Q000378:metabolism*
chemical_list: D004791:Enzyme Inhibitors; D009569:Nitric Oxide; D011374:Progesterone; D010121:Oxytocin; D015237:Dinoprost; D019001:Nitric Oxide Synthase; D019331:NG-Nitroarginine Methyl Ester