Circadian variation of the Ca2+ -PTH curve during hypercalcaemia in dogs.
To test the hypothesis that the parathyroid hormone (PTH) response to hypercalcaemia is influenced by circadian rhythms, the Ca2+ -PTH curve was studied in six dogs after infusion of CaCl2 (0.66 mEq/kg/h) at daytime (09:00 h) and at night-time (21:00 h). Plasma Ca2+ and PTH values measured before or after CaCl2 infusion were not different at day and at night. However, in the recovery from hypercalcaemia, PTH concentrations were significantly lower (P < 0.05) at 21:00 h (23 +/- 7.5 pg/ml at Ca2+ = 1.30 mm) than at 09:00 h (38.8 +/- 6.9 pg/ml at Ca2+ = 1.30 mm). In addition, the Ca2+ -PTH curve showed hysteresis at daytime (for the same Ca2+ concentration, PTH values were higher during recovery than during induction of hypercalcaemia) but not at night-time (PTH values were lower during recovery than during induction of hypercalcaemia). In conclusion, a circadian variation in the PTH secretory pattern during recovery from hypercalcaemia has been identified in dogs.
Department Medicina y Cirugía Animal, Universidad de Córdoba, Campus Rabanales, Ctra. Madrid-Cádiz km 396, 14014 Córdoba, Spain.
V
V
Domingo
I
I
López
F J
FJ
Mendoza
M
M
Rodríguez
E
E
Aguilera-Tejero
J C
JC
Estepa
D000818:Animals; D019540:Area Under Curve; D002118:Calcium / Q000097:blood*; D002122:Calcium Chloride / Q000494:pharmacology*; D002940:Circadian Rhythm / Q000502:physiology*; D004283:Dog Diseases / Q000378:metabolism; D004285:Dogs / Q000502:physiology*; D005260:Female; D006934:Hypercalcemia / Q000378:metabolism / Q000662:veterinary; D008297:Male; D010281:Parathyroid Hormone / Q000097:blood*
D010281:Parathyroid Hormone; D002122:Calcium Chloride; D002118:Calcium