Riassunto
Gli AA. hanno studiato l’effetto della somministrazione cronica di prolattina sulla glicemia e sui livelli sierici dell’IRI e dei NEFA, in cani normali, prima e durante IVGTT. Essi hanno osservato che la somministrazione cronica di prolattina: 1) non modifica i livelli glicemici e di IRI, mentre produce soltanto un lieve e non significativo aumento nella concentrazione sierica dei NEFA; 2) induce una moderata diminuzione della risposta glicemica nei primi 15 min dopo il carico di glucosio, mentre la glicemia media, il valore k ed i livelli sierici di IRI non risultano modificati; 3) accelera lievemente sia la caduta della NEFAemia che si osserva per effetto del carico, sia la sua risalita verso i valori basali dopo il raggiungimento di un minimo, e ciò nonostante la presenza di elevati livelli glicemici ed insulinemici. In cani sottoposti a trattamento cronico con prolattina, la NEFAemia è più elevata di quella che si osserva in animali di controllo non trattati nella fase finale del test, allorché i livelli glicemici ed insulinemici sono già tornati ai valori di partenza. Viene discusso il significato fisiologico di tali variazioni.
Résumé
On a étudié l’effet d’une thérapie chronique avec prolactine sur la glycémie et les niveaux d’insuline sérique immunoréactive et des acides gras libres des chiens normaux à jeun, avant et pendant une épreuve de tolérance au glucose i.v. On a observé que: 1) la thérapie semble ne pas affecter chez ces animaux à jeun les niveaux de glucose sanguin et d’insuline sérique immunoréactive et produit seulement une légère mais insignifiante élévation de la concentration des acides gras libres sériques; 2) quoique la thérapie induit une légère déscente des niveaux de la glycémie pendant les premières 15 min après la surcharge de glucose, ni la glycémie moyenne pendant l’épreuve ni le k du glucose n’ont pas été affectés; la courbe d’insuline sérique immunoréactive pendant l’épreuve s’est maintenue également inalterée; 3) la thérapie accélère légèrement la chute de la concentration des acides gras libres sériques suivant la surcharge de glucose; le retour à la ligne de base après une descente au minimum est aussi accéléré par la thérapie en dépit des hauts niveaux d’insuline sérique et de glucose sanguin; à la fin de l’expérience la concentration des acides gras libres sériques est definitivement surnormale, pendant que la glycémie et l’insulinémie sont déjà revenues à la ligne de base, chez les chiens traités. La signification physiologique de ces changements est discutée.
Resumen
Se estudió el efecto del tratamiento crónico con prolactina sobre los niveles de glucemia, insulina sérica inmuno-reactiva y ácidos grasos libres en perros normales en la condición postabsorptiva, antes y durante una prueba i.v. de tolerancia a la glucosa. Se observó: 1) en la condición post-absorptiva la terapia no afectó ni los niveles de glucemia ni los de insulina sérica inmuno-reactiva, pero sí indujo un muy pequeño aumento, no significativo, en la concentración de ácidos grasos libres circulantes en estos animales; 2) el tratamiento provocó una moderada disminución en los niveles de glucemia alcanzados durante los primeros 15 min luego de la sobrecarga de glucosa, pero no afectó la glucemia promedio durante la prueba, ni el valor k, ni tampoco el perfil de insulina sérica inmuno-reactiva; 3) el tratamiento aceleró levemente la caída de los niveles de ácidos grasos libres por la sobrecarga glucosada, como así también su retorno a la línea de base luego de pasar por un mínimo, a pesar de los elevados niveles de glucemia e insulinemia existentes. La concentración de ácidos grasos libres en suero de los perros tratados con prolactina crónicamente fué mayor que en los controles no inyectados al fin de la prueba, momento en que la glucemia e insulinemia habían retornado a sus valores basales. Se discute el significado fisiológico de todos estos cambios ocasionados por la hormona.
Zusammenfassung
Die Wirkung einer chronischen Prolactinbehandlung auf den Blutzucker, das immunologisch messbare Seruminsulin und die freien Fettsäuren wurde an normalen Hunden im post-absorptiven Zustand und vor und nach intravenöser Glukosebelastung verfolgt. Folgendes wurde beobachtet: 1) im post-absorptiven Zustand hatte die Behandlung keinen Einfluss auf Blutzucker und Serum IRI, bewirkte aber einen sehr bescheidenen, nicht signifikanten Anstieg der zirkulierenden FFA; 2) die Behandlung bewirkte eine mässige Verringerung der in den ersten 15 Min. nach der Glukosebelastung erreichten Blutzuckerwerte, ohne jedoch den mittleren Blutzuckerspiegel oder das IRI-Profil der Probe zu beeinflussen; 3) die Behandlung beschleunigte in geringem Ausmass den FFA-Abfall nach der Glukosebelastung wie auch nach Erreichung eines Minimuns die Rückkehr zum Ausgangswert trotz der hohen Blutzucker- und Seruminsulin-Werte. Am Ende der Probe, d.h. im Moment, wo Blutzucker und Insulinämie zu den Ausgangswerten zurückgekehrt sind, war die FFA-Konzentration im Serum der mit Prolactin behandelten Hunde höher als die der unbehandelten Tiere. Die physiologische Bedeutung dieser von dem Hormon verursachten Veränderungen wird besprochen.
Summary
The effect of chronic prolactin treatment on blood sugar, serum immunoreactive insulin and free fatty acid levels has been studied in normal dogs in the post-absorptive condition and during an i.v. glucose tolerance test. It was observed that: 1) the chronic administration of prolactin failed to affect either blood sugar or serum immunoreactive insulin levels in these animals in the post-absorptive condition and induced a very minor non-significant increase in serum free fatty acid concentration; 2) although prolactin chronic administration induced a moderate reduction in the blood sugar response in the first fifteen min after the glucose load, the average glucose level, kglucose, and serum IRI profile were unaffected; 3) prolactin administration slightly accelerated the fall of FFA levels during glucose administration as well as the return to baseline values in spite of the high blood glucose and insulin levels. In dogs having undergone chronic prolactin treatment the serum FFA concentration was higher than in non injected animals in the final stages of the test, i.e. at the moment when blood glucose and insulin had returned to basal levels. The physiological significance of these changes is discussed.
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This work was partially supported by theConsejo Nacional de Investigaciones Científicas y Técnicas, Argentina, Res. Grant. no. 2304-D.
Established Investigator,Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina.
Post-Graduate Fellow, University of Buenos Aires.
Traduzione a cura degli AA.
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Renauld, A., Sverdlik, R.C. & Andrade, L.L. The effect of chronic prolactin administration upon the blood sugar, insulin and free fatty acid response to a glucose load in the dog. Acta diabet. lat 10, 1286–1299 (1973). https://doi.org/10.1007/BF02590715
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DOI: https://doi.org/10.1007/BF02590715