Pancreatic Insulin Content of Nonpregnant, Pregnant and Postpartum Rats and the Developing Rat Fetus

Rishi, Surendra; Golob, E; Becker, Kenneth L.; Shah, Narendra J.

doi:10.2337/diab.18.5.268

Cited by 34 publications

(14 citation statements)

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“…This discrepancy in the two assays is probably related to the heterogeneity in the sample and standard. For example, the assay levels of Clark and Rutter (6) in the late embryonic pancreas agree well with earlier studies using beef insulin standards (20), whereas the insulin content of the late embryonic pancreas found in the present study agrees with those using homologous rat insulin as a standard (21,22 (20), using a less sensitive immunoassay, measured insulin levels during the late embryonic stages and by a linear extrapolation predicted the initiation of insulin synthesis between days 16 and 17. Grillo (23), in contrast, using an immunofluorescence method, reported the presence of insulin earlier in development, just at the beginning of the dramatic increase in specific activity.…”

supporting

confidence: 91%

“…In the current procedure, dilutions of reagents, standards, and samples are made with 0.5% crystalline bovine-serum albumin (Miles Laboratories) in 0.05 M phosphate (pH 7.0). The assay is carried out in three successive stages on each sample: I (40, [18][19][20][21][22][23][24] Ag per assay tube produced a low, yet significant, displacement of labeled hormone (insulin or glucagon). However, the lowest specific activities of glucagon determined required no more than 20 ug of total pancreatic protein; the lowest levels of insulin determined required less than 10 ug of total protein.…”

mentioning

confidence: 99%

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Early Differentiation of Glucagon-Producing Cells in Embryonic Pancreas: A Possible Developmental Role for Glucagon

Rall

Pictet

Williams

et al. 1973

Proc. Natl. Acad. Sci. U.S.A.

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Glucagon and insulin are first detectable at the onset of rat pancreas organogenesis. Initially, the specific activity of glucagon is approximately 100-fold higher than that of insulin. At this early stage, endocrine storage granules, similar to a granules, are identifiable in electron micrographs. The granule characteristics, as well as the relative hormone levels, suggest that the early population of differentiated endocrine cells is in fact composed of glucagon-producing (A) cells. This high level of glucagon is present in the embryo much earlier than the metabolic processes thought to be controlled by this hormone. Moreover, glucagon-producing cells may be the first endocrine cells to differentiate. Other known endocrine products accumulate later, during the terminal stages of organogenesis. These observations suggest that glucagon may have a regulatory function in early embryogenesis.The islets of the differentiated rat pancreas contain A and B cells, which are responsible for the production of glucagon and insulin, respectively, and D cells, whose function has yet to be defined. Until recently, the endocrine cells have been assumed to differentiate well after the appearance of the pancreatic diverticulum (3-5). However, Clark and Rutter (6), using a sensitive immunoassay, detected low levels of insulin at the time of the initial formation of the pancreatic diverticulum. Moreover, Wessells and Evans (7) (8) were decapitated, and the embryos of an appropriate gestational age were transferred to dissecting dishes containing Earle's balanced salt solution and 1.0% bovine-serum albumin. Pancreatic rudiments, excluding most of the associated mesenchyme, were excised and placed in polyethylene tubes (microfuge tubes, Spinco) on dry ice. The samples were stored at -70°until the time of assay, when they were thawed and subsequently sonicated in an aliquot of glass-distilled water. The crude homogenates were immediately monitored for hormone activity and protein content. Routinely, three dilutions were made of each sample, and each dilution was assayed in duplicate.Insulin Assay. Insulin was assayed according to a micromodification of the double-antibody technique of Morgan and Lazarow (9). Previously (6) beef insulin was used as a standard, while our more recent studies use the homologous rat insulin and a different combination of reagents to enhance the precision and sensitivity of the assay. In the current procedure, dilutions of reagents, standards, and samples are made with 0.5% crystalline bovine-serum albumin (Miles Laboratories) in 0.05 M phosphate (pH 7.0). The assay is carried out in three successive stages on each sample:

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supporting

confidence: 91%

mentioning

confidence: 99%

Early Differentiation of Glucagon-Producing Cells in Embryonic Pancreas: A Possible Developmental Role for Glucagon

Rall

Pictet

Williams

et al. 1973

Proc. Natl. Acad. Sci. U.S.A.

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“…The pancreatic insulin level was highest in 10-day-old control rats and decreased to adult levels between 15 and 25 days of age. A high insulin concentration in the pancreas of neonatal rats has been re ported by others [24], Previously published data indicate that the high pancreatic insulin the second dose ( fig. 1).…”

Section: Age-related Differences In the Susceptiblity Of Endocrine Pamentioning

confidence: 99%

Postnatal Changes in the Insulin-Depleting Action and Disposition of Cyproheptadine in Rats

Chow¹,

Fischer²

1991

Dev Pharmacol Ther

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The relationship between age-related differences in cyproheptadine (CPH)- induced alteration of endocrine pancreas function and the disposition of the drug was examined in this study. Various doses of CPH (5, 11, 22.5 or 45 mg/kg) were given orally once daily for 2 days to 10-, 15-, 25- and 50-day-old rats. Pancreatic and serum insulin measured 24 h after the second dose showed a drug-dependent decline, and the extent of this effect was dependent on the dose administered and the age of the animal. In 50-day-old rats, a significant reduction in pancreatic and serum insulin was detected only after high doses (22.5 and 45 mg/kg) of the drug. However, in 10- and 15-day-old rats, the effects were observed after the lowest dose (5 mg/kg). In separate experiments, the concentrations of CPH and its active metabolites, desmethylcyproheptadine (DMCPH), desmethylcyproheptadine-10,11-epoxide (DMCPH-epoxide) and cyproheptadine-10,11-epoxide (CPH-epoxide), were measured in the pancreas, liver and lung of neonatal and young rats at various times after the second dose of CPH (11 mg/kg). In the younger age groups (10- and 15-day-olds), there were significantly higher tissue levels of unchanged drug at all times examined. Certain of the drug metabolites known to be inhibitors of insulin synthesis had higher and/or more prolonged tissue concentrations in younger animals. For example, the metabolite CPH-epoxide was found only in tissues from younger age groups. Twenty-four hours after the second dose of CPH, no drugderived product was present in tissues of 25- and 50-day-old rats, whereas significant amounts of DMCPH-epoxide, a potent CPH metabolite inhibiting insulin synthesis, was detected in the tissues of 10- and 15-day-old rats. The data show that there are age-related differences in the susceptibility of pancreatic B cells to the actions of CPH, and that these differences are associated with age-related changes in the disposition of the drug.

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“…Insulin was extracted from the fetal pancreas by acid-ethanol [7] and estimated as described previously [8], Rat insulin (supplied by Dr. M. Root, Eli Lilly Co.. Indianapolis, Ind., USA) was used as standard and the data expressed as microunits insulin per milligram wet weight of the pancreas. All data were calculated as mean values ± SEM and analyzed for statistical dif ference by Anova.…”

Section: Methodsmentioning

confidence: 99%

Ultrastructure of Insulin Secretory Granules and Insulin Content of Fetal Pancreas Exposed to Ethanol in utero in the Rat

Singh¹,

Yokoo²,

Yokoo³

et al. 1986

Neonatology

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Fetal rat pancreata exposed to ethanol in utero were examined for morphometric analysis of insulin secretory granules and insulin content. The β-cells contained both dark and light granules, and their volume density was unaltered by maternal ethanol ingestion during pregnancy. The insulin content of pancreata of newborn rats was nearly equal in control and experimental animals. The study indicates no adverse effect of maternal ethanol ingestion on fetal pancreatic insulin concentration and insulin secretory granules.

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Pancreatic Insulin Content of Nonpregnant, Pregnant and Postpartum Rats and the Developing Rat Fetus

Cited by 34 publications

References 0 publications

Early Differentiation of Glucagon-Producing Cells in Embryonic Pancreas: A Possible Developmental Role for Glucagon

Early Differentiation of Glucagon-Producing Cells in Embryonic Pancreas: A Possible Developmental Role for Glucagon

Postnatal Changes in the Insulin-Depleting Action and Disposition of Cyproheptadine in Rats

Ultrastructure of Insulin Secretory Granules and Insulin Content of Fetal Pancreas Exposed to Ethanol in utero in the Rat

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