ABSTRACT
La galanina es un péptido que consta de 29 aminoácidos originalmente aislado de intestino de porcino. Se sintetiza inicialmente como parte de una proteína mayor precursora (preprogalanina). En todas las especies, la porción N-terminal se conserva completamente. Sin embargo, la región C-terminal se modifica ligeramente. Algunas de las características fisiológicas de la galactina son contraer preparaciónes aisladas de fundus, ileo, colon y vejiga urinaria e induce hiperglucemia ligera y sostenida. Su administración estimula el consumo de alimento y tiende a aumentar las concentraciones plasmáticas de la hormona de crecimiento, de prolactina y disminuye la concentración de dopamina. Los estrógenos estimulan dramáticamente la síntesis de ARNm para la galanina y la subsecuente síntesis del péptido. La amplia distribución de la inmunoreactividad semejante a galanina y su localización en los gránulos neurotransmisores sugieren que la galanina puede funcionar como neurotransmisor. Sin embargo, la detección de la inmunorreactividad semejante a galanina después de la estimulación con 17 ß-estradiol sugiere que la galanina hipofisiaria tiene un blanco a distancia, por lo que puede ser una hormona adicional de la hipófisis anterior. Debido a que la galanina se ha localizado en los tejidos reproductivos, parece jugar un papel mediado por estrógenos en la función hipotalámica e hipofisiaria
Subject(s)
Galanin , NeuropeptidesABSTRACT
Large superovulatory doses of gonadotrophins result in reduced fertility in laboratory and large domestic animals and it has been postulated that some of the superovulated oocytes are derived from abnormal follicles wich would not ovulate under normal physiological stimuli. Follicular growth, follicular maturation and atresia, ovulation and the nidation of the fertilized oocute require intense tissue remodelation which can be accomplished only through the action of hydrolytic enzymen. We have studied the activities and sub-cellular distribution of three lysosomal ensymes (acid phosphatase, N-acetyl-ß-D-glucosaminidase and ß-glucuronidase) in the follicular fluid, granulosa and theca cells of preovulatory follicles and in the endometrial tissue of immature Wistar rats injected with 4 (control) or 40 (superovulated) IU of pregnant mare serum gonadotrophin (PMSG). Enzyme activities were from four to ten time higher in theca than in granulosa cells. This difference was particularly important in the case of ß-glucuronidase. Large preovulatory follicles tended to have higher activities of lysosomal ensymes in the free fraction of all the compartments studied. This difference was remarkable in theca cells where free enzymes could be required to help ovulation. Forty IU of PMSG induced higher activities of acid phosphatase in theca and granulosa cells than 4 IU, but in endometrial tissue this latter dose of PMSG was more efficient to induce higher activities of this enzyme. The endometrial bound fraction of N-acetyl-ß-D-glucosaminidase was almost three times higher than the free activity. This behavior was also observed in endometrial ß-glucosaminidase but only in the control rats. The results observed in follicular fluid were less homogeneous. The activities of glucosaminidase and acid phosphatase were two to three times higher in rats overstimulated with 40 IU of PMSG than int he controls rats, whereas the activities of ß-glucuronidase were lower in the superovulated rats. Our results suggest that alterations in the process of tissue remodeling required for ovulation of mature, normal oocytes and for nidation of the fertilized ovum may be important factors to explain pregnancy failure in the PMSG superovulated female