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Functional coupling between the active transport of glucose and the secretion of intestinal neurotensin in rats.
Author(s) -
Dakka T,
Cuber J C,
Chayvialle J A
Publication year - 1993
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1993.sp019841
Subject(s) - medicine , endocrinology , chemistry , ouabain , phloretin , guanethidine , sodium , stimulation , biochemistry , organic chemistry
1. In this study, the mechanisms involved in the release of neurotensin‐like immunoreactivity (NTLI) by glucose were investigated with the isolated, vascularly perfused rat jejunoileum preparation. 2. Luminal infusion of glucose (1‐250 mM) produced a sharp and sustained release of NTLI in the intestinal venous effluent. The first significant response was observed with 5 mM glucose and the release reached a maximum under 250 mM glucose with a plateau secretion at 500% of basal. 3. There was no significant difference in the ability of galactose and 3‐O‐methylglucose to release NTLI when compared to glucose, but alpha‐methylglucose, mannose, 2‐deoxyglucose and fructose did not stimulate NTLI release. 4. Luminal infusion of 5 mM phloridzin reduced the glucose‐induced release of NTLI by 90%. Intra‐arterial infusion of glucose (25 mM) or of phloretin (20 microM) had no significant effect on the glucose‐evoked NTLI secretion. 5. Intra‐arterial infusion of ouabain (1 mM) produced a dramatic increase (at about 1500% of basal) in portal NTLI although it drastically reduced intestinal absorption of glucose. 6. Intra‐arterial infusion of tetrodotoxin (1 microM), atropine (10 microM), verapamil (50 microM) or nifedipine (50 microM) did not modify the glucose‐induced NTLI secretion. 7. Intra‐arterial infusion of forskolin (2‐20 microM) evoked a prompt and well‐sustained secretion of NTLI which was increased to a mean value of 800% of basal with the highest dose tested. 3‐Isobutyl‐1‐methylxanthine (IBMX, 10‐100 microM) also stimulated the secretion of NTLI (maximal increase at 725% of basal at 100 microM). In contrast, intra‐arterial infusion of 4‐beta‐phorbol 12‐myristate, 13‐acetate (PMA, 0.05‐0.5 microM) had no effect on NTLI release. 8. IBMX (10‐100 microM) synergistically enhanced NTLI responses induced by 250 mM glucose; the integrated response of NTLI release was 3‐ to 5‐fold higher than the sum of individual responses produced by the same stimulants given separately. 9. It is concluded that the carbohydrate‐induced NTLI release is related to the active, sodium‐dependent hexose transport, but not to the carbohydrate catabolic pathway. Furthermore, the intramural nerves and L‐type calcium channels are not involved in the glucose‐induced NTLI secretion. Finally, the secretory activity of the intestinal N cell seems to be mainly stimulated through a cAMP‐dependent pathway.