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En becerras prepúberes, la kisspeptina-10 (KISS-10) estimula la liberación de hormona luteinizante (LH) y hormona foliculoestimulante (FSH), pero su acción en la hormona del crecimiento (GH) es inconsistente. La hipótesis fue que en becerras prepúberes la magnitud de liberación de LH, FSH y GH en respuesta a KISS-10 es determinada por la dosis y las concentraciones endógenas de IGF-I y leptina. Se usaron 20 becerras prepúberes (100-232 kg de peso y 7-11 meses de edad), mismas que recibieron un bolo i.v. de 5 o 50 µg de KISS-10/kg de peso. Ambas dosis de KISS-10 indujeron un incremento de LH y FSH, más no de GH. La dosis de 50 µg de KISS-10 indujo un área bajo la curva de LH y una duración del incremento de FSH mayores (P0.05). De la misma forma, las concentraciones de leptina no determinaron (P>0.05) la magnitud del incremento de LH y FSH ni las concentraciones de GH pos tratamiento. En conclusión, la GH no respondió a ninguna dosis, pero la FSH y la LH fueron sensibles al aumento de dosis de KISS-10. Además, la magnitud de respuesta de LH a KISS-10 fue determinada por las concentraciones endógenas de IGF-I, pero no de leptina.

El objetivo fue evaluar la respuesta de LH, FSH y GH a kisspeptina-10 (KISS) en becerras prepúberes de distintas edades, y su asociación con IGF-I, E2 y leptina circulantes. A 21 becerras de 4, 7 y 11 meses de edad se les aplicó una inyección i.v. de 5 µg de KISS/kg de peso. En suero obtenido de la yugular (cada 15 min, 4 h pre hasta 4 h post-KISS) se cuantificó LH, FSH y GH. En nueve muestras (tres pre y seis post-KISS) se determinó IGF-I, leptina y estradiol (E2). En todas las becerras aumentó la LH post-KISS, con un valor máximo (6.1±1.3a, 7.2±1.3a, 11.6+1.3b ng/ml) y duración de respuesta (64.3±20a, 92±20b, 132.9+20c min) que aumentó (P

In prepubertal heifers, kisspeptin-10 (KISS-10) stimulates the release of the luteinizing hormone (LH) and the follicle-stimulating hormone (FSH) but the growth hormone (GH) response is inconsistent. The hypothesis of this study was that in prepubertal heifers, the release of LH, FSH and GH in response to KISS-10 is determined by dose and by endogenous levels of IGF-I and leptin. Twenty heifer calves (100-232 kg of body weight and 7-11 mo of age) received an i.v. injection of 5 or 50 μg of KISS-10/kg of body weight (low and high dose, respectively). The high dose of KISS-10 induced a greater (P<0.05) response of LH (area under the curve) and FSH (duration) than the low dose. IGF-I was negatively associated (P<0.05) to LH in response to the high dose of KISS-10 but IGF-I was not associated with LH in calves treated with the low dose (P>0.05). The magnitude of FSH response as well as GH serum concentrations after KISS-10 were not altered by IGF-I levels (P>0.05). Similarly, leptin concentrations were not associated (P>0.05) with the magnitude of LH and FSH response or GH concentrations after KISS-10. In conclusion, GH did not respond to any dose of KISS-10 but FSH and LH were sensitive to an increment in the KISS-10 dose. Additionally, the magnitude of response of LH to KISS-10 was determined by endogenous levels of IGF-I but it was not associated with levels of leptin. [ABSTRACT FROM AUTHOR]

To evaluate effects of age on the response of LH, FSH and GH to kisspeptin-10 (KISS) in prepubertal heifers and its association with circulating levels of IGF-I, estradiol (E2) and leptin, 21 heifer calves that were 4, 7 or 11 mo old, received an iv injection of KISS (5 µg/kg). LH, FSH and GH were quantified in blood serum taken every 15 min (4 h pre- and 4 h post-KISS-10). In three preand six post-KISS samples, IGF-I, leptin and E2 were determined. All heifers responded to KISS with an LH increment but the response magnitude differed among groups since maximum value was higher (P <0.05) in 11 mo (11.6+1.3 ng/ml) than in 7 mo (7.2±1.3 ng/ml) and 4 mo (6.1±1.3 ng/ml) old calves. Duration of response differed (P <0.05) among ages (11 mo=132.9+20 mina; 7 mo=92±20 mina,b; 4 mo=64.3±20 minb). For FSH, all and 11 mo calves responded to KISS but only 71.4 % of 4 mo did. In GH, 71.4 % of 4 mo and 85.7 % of 7 mo calves responded to KISS whereas 100 % of 11 mo animals responded. FSH and GH did not differ among age groups. The 11 mo heifers had the highest IGF-I and E2 but the lowest leptin levels. In conclusion, KISS evokes LH increments in all calves 4 to 11 mo old, but the response increases with age in association with high circulating IGF-I and E2 and low leptin. The response of FSH and GH to KISS is not influenced by age or variations in circulating IGF-I, E2 or leptin. [ABSTRACT FROM AUTHOR]