The Occurrence of Insulin in the Pancreas of Foetuses of Some Rodents

Grillo, T. Adesanya Ige

doi:10.1677/joe.0.0310067

Cited by 41 publications

(28 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…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. Grillo et al (24), as well, measured the level of glucagon-like material based on the activation of glycogen phosphorylase in rabbit-liver slices and reported its presence as early as the 14th day.…”

mentioning

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%

See 1 more Smart Citation

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.

View full text Add to dashboard Cite

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:

show abstract

mentioning

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.

View full text Add to dashboard Cite

show abstract

“…The synthesis and storage of insulin in the pancreatic B cells of the rat appear to start during the 1 l t h day of gestation (36,59). However, the precise time at which the insulin-releasing mechanism begins to function has not been determined and may vary with the nature of the stimulus.…”

mentioning

confidence: 99%

The Synthesis and Release of Insulin in Fetal, Nursing and Young Adult Rats: Studies in Vivo and in Vitro

et al. 1975

View full text Add to dashboard Cite

ExtractThe secretion of insulin in vivo and its synthesis and release by pancreatic islets in vitro were studied in rats at various stages of development. An oral glucose load caused a rapid and significant increase in the serum insulin level of pregnant rats and a slower response in their 21-day-old fetuses. Circulating free fatty acids (FFA) decreased in the dams, but did not change in the fetuses. A relative glucose intolerance was found in pups 1 hr, 5 days, and 10 days after birth. This was accompanied by delayed insulin response and by little or no decrease of circulating FFA. After weaning, the glucose tolerance and the insulin and FFA responses gradually improved. The oral administration of a 10-amino acid mixture caused a greater insulin release in newborn and nursing rats than in 21-day-old fetuses or inyoung adult rats. Total serum lipids were higher in I-, 5-, lo-, and 20-day-old rats than in fetuses and adult animals, whether fed or fasted, but 18 hr of fasting decreased total lipids and phospholipids in all age groups. Thus, the age of relative hyperlipidemia corresponded with that of relative glucose intolerance. The secretion of insulin in vitro by pancreatic islets of 5-, lo-, 20-, 30-, and 45-day-old rats increased significantly when the concentration of glucose in the incubation medium was increased from 30 to 300 mg/ml. The islets of 30-and 45-day-old rats secreted the largest amount of insulin. The insulin content of pancreatic islets was higher and the percentage of insulin secreted in relation to the hormonal content was smaller in the islets of nursing rats. Islets of fetal, nursing, and adult rats incorporated L -[ 4 ,~-~~] l e u c i n e into proinsulin and insulin, but the conversion of proinsulin to insulin was minimal in the 1-day-old rat. This incorporation was greater when the glucose concentration of the medium or the incubation time were increased. Thus, birth appears to be associated with a temporary decrease in the ability to release insulin and to dispose of an exogenous glucose load. Speculation large masses of insulin-responsive tissues. Gluconeogenesis continues to be a major source of glucose throughout the nursing age, when the animal consumes a diet rich in protein and fat and low in carbohydrate. Although the fetal pancreas can synthesize insulin, the mechanism for its release and hence the ability to dispose of a glucose load do not reach full maturity until weaning, when the dietary intake of carbohydrate increases and the level of serum lipids decreases toward I the values characteristic of the adult animal. 1The synthesis and storage of insulin in the pancreatic B cells of the rat appear to start during the 1 l t h day of gestation (36, 59). However, the precise time at which the insulin-releasing mechanism begins to function has not been determined and may vary with the nature of the stimulus. Thus, the fetal pancreas, even though insensitive to glucose (4, SO), may respond to other substances (see Reference 37) so that, toward the end of pregnancy, the fetal serum ...

show abstract

“…Insulin has also been detected in the fetal pancreas before granule formation (Grillo, 1964;Milner, 1969;Willes ^ , 1969). Insulin production has been noted in 3-cell tumors without B-granule formation (Steiner and Cunningham, 1967).…”

Section: Morphologic Details Of 3-cell Secretionmentioning

confidence: 98%

“…The use of these models has been proposed for clinical evaluation of diabetic subjects (Ackerman e;t al., 1964;Cerasi, 1967).…”

mentioning

confidence: 99%

Suppression of insulin secretion during spontaneous and induced hypocalcemic states

Witzel

View full text Add to dashboard Cite

The Occurrence of Insulin in the Pancreas of Foetuses of Some Rodents

Cited by 41 publications

References 10 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

The Synthesis and Release of Insulin in Fetal, Nursing and Young Adult Rats: Studies in Vivo and in Vitro

Suppression of insulin secretion during spontaneous and induced hypocalcemic states

Contact Info

Product

Resources

About