SciELO - Scientific Electronic Library Online

 
vol.32 número2Sensibilidad tisular a la insulina antes, durante y después de un ayuno en ovejas prepúberesEfectos del tiempo de transporte de novillos previo al faenamiento sobre el comportamiento, las pérdidas de peso y algunas características de la canal índice de autoresíndice de materiabúsqueda de artículos
Home Pagelista alfabética de revistas  

Servicios Personalizados

Revista

Articulo

Indicadores

Links relacionados

Compartir


Archivos de medicina veterinaria

versión impresa ISSN 0301-732X

Resumen

RECABARREN, S. E. et al. Effect of melatonin on the pulsatile luteinizing hormone and growth hormone secretion in ewe lambs under food restriction. Arch. med. vet. [online]. 2000, vol.32, n.2, pp.147-156. ISSN 0301-732X.  http://dx.doi.org/10.4067/S0301-732X2000000200002.

The aim of the present work was to characterize the pulsatile LH and GH secretion in food restricted Suffolk ewe lambs (n=5, R-MEL group) receiving daily oral administration of melatonin (3mg/20 mL, at 16:00 h), at 20-26- and 30 weeks of age, after 4,10 and 14 weeks of food restriction. Melatonin treatment was initiated at 10 weeks of age. Food restricted lambs of the same age, without melatonin treatment acted as comparative group (n=6, R-SOL). Blood samples were collected from a jugular vein by means of an indwelling catheter at 10 min-intervals for 6 hours, from 09:00 h. LH and GH were measured by radioimmunoassay. Plasma concentrations of both hormones were analyzed by the Cluster program to define pulse frequency (n° pulses/6h), and pulse amplitude (ng/mL). The transversal mean of LH and GH was also calculated (ng/mL/6h). In the R-MEL group, the transversal mean of LH tended to increase from 0.35± 0.04 in 20 weeks old lambs to 0.61± 0.15 ng/mL/6h in 30 weeks old lambs while remained unchanged in the R-SOL group: 0.34± 0.03 and 0.25±0.05 ng/mL/6h, respectively. LH pulse frequency did not change and was not different between both groups. LH pulse amplitude tended to be higher in R-MEL than in R-SOL lambs at 30 weeks of age: 0.76± 0.28 and 0.38± 0.09 ng/mL, respectively (P<0.07). In contrast to the low effect of melatonin on LH secretion, the transversal mean and the GH pulse amplitude were significantly modified by the melatonin treatment. R-MEL lambs had mean concentrations of 3.28±1.14, 6.25±1.88 and 7.26±1.57 ng/mL/6h at 20,26 and 30 weeks, respectively while R-SOL lambs had 15.69±1.37 (P<0.01), 13.25±2.66 (P<0.02) and 19.12±3.88ng/mL/6h (P<0.03), respectively. Pulse amplitude was also lower in R-MEL than in R-SOL lambs at 20, 26 and 30 weeks of age. GH pulse frequency was not different between groups and ages. Results suggest that melatonin is involved in the control of GH secretion in growing sheep, overpassing the metabolic effect of food restriction on GH secretion. However, in the case of LH, the metabolic impact of food restriction is not completely overcome by the stimulatory effect of melatonin on the LHRH/LH secretion, suggesting that the metabolic status of the growing sheep should be in concert with the photoperiod to coordinate the initiation of puberty

Palabras clave : melatonin; LH and GH secretion; food restriction; prepubertal development.

        · resumen en Español     · texto en Español

 

Creative Commons License Todo el contenido de esta revista, excepto dónde está identificado, está bajo una Licencia Creative Commons