title: Influences of season and of temperature, photoperiod, and subcutaneous melatonin infusion on the glomerular filtration rate of ewes.
abstract: Influences of season and of temperature, photoperiod, and subcutaneous melatonin infusion on glomerular filtration rate (GFR) were measured in ewes. There was a seasonal difference of GFR between summer (June-August) and winter (December-February) in Tokyo (35 degrees, 35' N); GFR was significantly (P < 0.05) higher in summer (4.2 +/- 0.3 ml/min/kg) than in winter (3.0 +/- 0.2 ml/min/kg). GFR was measured after exposure to three types of photoperiod, 24L:0D, 12L:12D, and 0L:24D, for 7 to 8 days. The value for GFR obtained at 20 degrees C was significantly lower (P < 0.05) with 0L:24D than with the other two photoperiodic conditions. GFR obtained during subcutaneous melatonin infusion (20 micrograms/hr for 16 hr/day for 7 days) with 24L:0D conditions was significantly (P < 0.05) lower (2.5 +/- 0.1 ml/min/kg) than without infusion (3.8 +/- 0.3 ml/min/kg) and was about the same as that obtained in animals under 0L:24D conditions. At 30 degrees C, GFR exhibited no difference between the 3 photoperiodic conditions and was always lower than that found at 20 degrees C. Possible influences of melatonin on GFR are discussed.
authors.affiliation: Department of Animal Physiology, Tokyo University of Agriculture, Setagaya, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Tsuda
authors.forename: M
authors.initials: M
authors.lastname: Ide
authors.forename: M
authors.initials: M
authors.lastname: Iigo
mesh_terms: D000818:Animals; D004326:Drinking; D005260:Female; D005919:Glomerular Filtration Rate / Q000187:drug effects* / Q000502:physiology*; D007263:Infusions, Parenteral; D007668:Kidney / Q000187:drug effects / Q000502:physiology; D008550:Melatonin / Q000008:administration & dosage* / Q000097:blood / Q000502:physiology; D017440:Photoperiod; D012621:Seasons; D012756:Sheep; D013696:Temperature
chemical_list: D008550:Melatonin