title: Kinetic studies and production rate of melatonin in pony mares.
abstract: The aims of the present study were to determine basic kinetic parameters and the nycthemeral production rate of melatonin in the horse. Seven pony mares were used for the kinetic studies. Five other pony mares were used under long and short days for the production rate studies. Melatonin was administered by intravenous, oral, and intragastric routes at different dose levels. The plasma melatonin clearance was 1.02 +/- 0.31 l.kg-1.h-1, and the volume of distribution was 0.89 +/- 0.53 l/kg for the 0.4 microgram/kg melatonin dose. The systemic availability after oral and intragastric administration was consistently low (< or = 10%). The hourly melatonin production rates during short (36 +/- 33.6 ng.kg-1.h-1) and long nights (42 +/- 24.0 ng.kg-1.h-1) were not significantly different. It is concluded that the oral dose of exogenous melatonin required to control reproductive pattern in horses would need to be 10 times higher than the nocturnal melatonin production (0.5 microgram/kg) to obtain a physiological plasma melatonin concentration.
authors.affiliation: Institut National de la Recherche Agronomique de Tours, Physiologie de la Reproduction des Mammifères Domestiques, Nouzilly, France.
authors.forename: D
authors.initials: D
authors.lastname: Guillaume
authors.forename: N
authors.initials: N
authors.lastname: Rio
authors.forename: P L
authors.initials: PL
authors.lastname: Toutain
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D005260:Female; D006736:Horses / Q000378:metabolism*; D007700:Kinetics; D008550:Melatonin / Q000096:biosynthesis* / Q000097:blood; D008954:Models, Biological; D009994:Osmolar Concentration
chemical_list: D008550:Melatonin