Enhancement of insulin secretory response to glucose-dependent insulinotropic polypeptide (GIP) by growth hormone in dogs

ABSTRACT: In the present work we examined the incretin role of gut glucose-dependent insulinotropic polypeptide (GIP) in the insulin overresponse to meal ingestion found in states of hypersomatotrophism. In this context, we studied IRI secretion after i.v. infusion of glucose alone (0.6 g/kg/h) and also combined with GIP (0.4 _g/kg/h) in dogs during the control period and after subcutaneous administration of bovine growth hormone (bGH, 1 mg/kg), in randomized experiments at fortnightly intervals. Plasma levels of immunoreactive b-GH (IRbGH) showed a comparable elevation at 24 h from each bGH injection. Coinciding with this rise, fasting plasma glucose was within the normal range and basal plasma levels of immunoreactive GIP (IR-GIP) remained unchanged. When GIP was given, there was a significant increase in IR-GIP plasma levels after 10 min of infusion, to a plateau near 200 pmol/l; the values were not influenced by concurrent administration of glucose with or without prior treatment with bGH. In the control observations, glucose infusion caused an insulin response area (IRA, pmol_min_l_1) of 3150_733. When GIP was co-infused with glucose, the IRA was enhanced to 6203_1380, p<0.005. After the administration of bGH, the infusion of glucose alone incresed the IRA to 9580_1446 (p<0.001) and to 15906_2943 (p<0.001) when GIP was co-infused with glucose. The data suggest that in this state of high circulating levels of growth hormone of short duration, the secretion of insulin in response to the stimulus of glucose alone and also combined with GIP is clearly enhanced. The findings therefore lend support for the explanation of the high insulin secretion evoked by food intake in growth hormone-treated dogs.

Efecto de la hormona somatotropica sobre la secrecion de insulina de perros cachorros / Effect of somatotropic hormone on insulin secretion in pups

En el presente estudio se abordó el efecto de la somatotropina de origen bovino (bSTH) en el perro cachorro. Se pbservó el perfil diario caracterizado por un incremento de la insulina inmunorreactiva sérica (IIR) a partir de las 6h de la administración subcutánea de bSTH, el cual se mantiene por 24h. La glicemia permaneció dentro de los límites normales observados en el periodo control, mientras que los ácidos grasos libres sufrieron un incremento significativo. La adminsitración intravenosa de glucosa, a las 24h de una segunda dosis de bSTH, prodyjo una excursión de la glucemia dentro de límites normales, con un exagerado aumento de la IIR, creando una situación que semeja los estados de resistencia insulínica. Los resultados señalan en el cachorro una respuesta cualitativamente similar a del perro adulto, en la cual la hiperinsulinemia debe jugar papel importante en el sostenimiento de la normoglicemia.

Estandarización de técnicas de aislamiento de islotes de langerhans de mamíferos grandes (perro y cochino) y vibilidad in vitro e in vivo: comunicación preliminar / Standarization

Se describe una técnica para el aislamiento de islotes de Langerhans de páncreas de perro y cochino, en la cual combinamos la digestión enzimática del tejido (por medio de la perfusión a través del ducto pancreático principal, una vez extraido el organo), disrupción mécanica y purificación de los islotes mediante un gradiente de densidad, comparando la viabilidad de los mismos tanto in vitro (perro y cochino) como in vivo (perro) obteniendo 350000 islotes/perro y 200000 islotes/cochino, con una pureza del 50-80 por ciento y se observó una disminución en los valores de glicemia en el perro una vez realizado el autotrasplante

Effect of glucose-dependent insulinotropic polypeptide (GIP) on insulin response to glucose in acromegalics

The pancreatic beta-cell response to stimulation with glucose and GIP, single and combined, was studied in acromegalics and in normal subjects. Acromegalics had higher IRI and GIP basal values with glucose levels and glucose disposal in the normal range. Further, acromegalics showed a greater IRI response to glucose, GIP and glucose combined with GIP. The results suggested that high growth hormone levels cause a greater activity of the entero-insular axis both in the basal state and after meal ingestion, as mimicked by GIP infusion. From these and previous observations, it can be assumed that growth hormone induces a facilitation of the IRI response to metabolite substrates and hormones