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Changes in canine plasma glucose, immunoreactive glucagon (IRG), pancreatic polypeptide (PP) and insulin (IRI) were studied during the acute development of diabetes mellitus after iv alloxan injection. 100 mg or 75 mg/kg body weight of alloxan was injected iv and blood was taken successively till one or two days later. Plasma glucose showed four phases: first immediate and moderate decrease appeared 30 min after injection, second initial hyperglycemic phase, third hypoglycemic and fourth diabetic ones. Plasma IRI had already increased to 182 +/- 60 microU/ml 10 min after injection and again began to increase after about 6 h, peaking to 134 +/- 49 microU/ml at 18 h. Plasma IRG began increasing gradually soon after alloxan injection. The initial value was 196 +/- 26 pg/ml and it increased to 534 +/- 144 pg/ml at 4 h during the initial hyperglycemic phase, then reached a higher level through the hypoglycemic and diabetic phases. The change in plasma PP was similar to that in IRG. The initial value was 256 +/- 95 pg/ml at 12 h after injection, peaking to 840 +/- 100 pg/ml in the hypoglycemic phase. Similar blunted values were obtained following 75 mg/kg alloxan injection. Thus not only plasma IRI but also plasma IRG and PP varied greatly during the acute development of alloxan diabetes and some contribution of IRG to the initial hyperglycemic phase was suggested.

The plasma responses of pancreatic polypeptide (PP), glucagon (IRG) and insulin (IRI) after administration of beef soup were studied in normal and alloxan diabetic dogs kept in a poor metabolic state for 4 weeks, and their regional levels in the pancreas were determined and compared at the uncinate process, head, body and tail. The plasma PP levels of the diabetic dogs were significantly higher than those of the normal dogs and they increased after beef soup administration in both groups. The plasma IRG levels did not change significantly after beef soup administration in either group, but significantly high levels were found in the diabetic dogs. The IRI content in the normal dog pancreas was highest at the tail, followed in order by the body, head and uncinate process, and was decreased to about one-tenth to one-fortieth in the alloxan diabetic dogs. On the other hand, the amounts of PP in the pancreas of both normal and diabetic dogs were greatest at the uncinate process, followed in order by the head, body and tail. In an inverse relationship with the PP findings, the IRG content in the pancreas was highest at the tail and lowest at the uncinate process in both kinds of dogs. The differences in both PP and IRG between diabetic and normal dogs were generally not significant. These results show that irrespective of the high plasma levels of PP and IRG in the diabetic dogs, their levels in the pancreas did not change significantly.

The acid saline extract (ASE) of rat submaxillary gland exerts a powerful degrading effect on 125I-glucagon. In order to study the degradation of other 125I-peptides by ASE and the effects of their inhibitors, 125I-pancreatic polypeptide (PP) and 125I-insulin were used together with 125I-glucagon. The degradation studies were done by the trichloroacetic acid (TCA) method or gel filtration. Besides 125I-glucagon, 125I-PP was found to be destroyed by ASE in the ordinary immunoassay system using the TCA method, but 125I-insulin was intact in the presence of ASE. Leupeptin, and to a lesser extent p-chloromercuriphenyl-sulfonic acid (PCMS) and N-ethylmaleimide, inhibited the destruction of 125I-glucagon or -PP under the TCA method. PCMS was especially protective at high concentrations, for example 16 mM. These findings were confirmed by gel filtration of the assay mixture. In the presence of leupeptin (0.4 mM) and PCMS (16 mM), no shift in the peak of labelled glucagon or PP occurred. Thus ASE degrades not only 125I-glucagon but -PP, and thiol proteinase inhibitors have a strong inhibitory action on them.

Twenty-four-hour variations of plasma hPP levels together with plasma glucose, IRI and GI levels were studied in four normal human subjects. Before examination, their food intakes were strictly controlled during two days' hospitalization. Plasma hPP values were assayed by a radioimmunoassay. They showed sharp peaks after each meal. Mean levels of hPP just prior to breakfast were 88 +/- 26 pg/ml (SEM), and the peak values of the plasma hPP one hour after each meal were 307 +/- 124 pg/ml, 398 +/- 77 pg/ml, and 544 +/- 118 pg/ml, respectively. During the nocturnal sleeping period the hPP levels were stable and returned to the fasting level of the previous morning. IRI increased significantly after each meal, but no significant change was found in plasma GI levels.

The amounts of insulin and pancreatic polypeptide (PP) in twenty four autopsied diabetic and nineteen nondiabetic human pancreases were determined and their relationship to the stability of the fasting serum glucose level was investigated. The PP content of the tail of the pancreas in diabetic and nondiabetic subjects was 9.55 +/- 2.41 and 7.71 +/- 1.52 micrograms/g pancreas, and that of the head of the pancreas was 16.86 +/- 5.51 and 15.82 +/- 5.38 micrograms/g, respectively. No significant differences in content were found between diabetic and nondiabetic pancreases. The PP content of the head pancreas of some diabetics and nondiabetics was higher than that of the tail. The insulin content of the tail of the diabetic pancreas was lower than that of the nondiabetic pancreas. In those diabetics where there was less than 0.5 U/g of insulin in the tail pancreas, the stability of the fasting serum glucose was very poor, indicating an unstable type of diabetes. There was a significant inverse correlation between standard deviation of FBS and the amount of insulin, but the PP content of the pancreas had no relation to the stability of the fasting serum glucose.

Responses of plasma pancreatic polypeptide (PP), glucagon (IRG) and insulin (IRI) after administration of beef soup were studied in normal and alloxan diabetic dogs and their regional content in the pancreas was determined in normal and four or twelve weeks alloxan diabetic dogs. Plasma PP levels of the diabetic dogs were significantly higher than those of the normal dogs and they increased after beef soup administration in both groups. Higher levels of IRG were also found in the diabetic dogs, although IRG increased significantly after beef soup ingestion only in normal dogs. The amounts of PP in the pancreas of normal and diabetic dogs were greatest at the uncinate process, followed in order by the head, body and tail. The IRG content in the pancreas was highest at the tail and lowest at the uncinate process in both dogs. The differences in both PP and IRG in pancreas between normal and diabetic dogs kept in a poor metabolic state for one or three months were not significant in any region of the pancreas. Immunocytochemical studies also suggested these findings. These results show that, irrespective of high plasma levels of PP and IRG in the diabetic dogs, their levels in the pancreas did not change significantly as also indicated by histological studies.

In order to know the degree of the destruction of peptide hormones in pancreatic tissue of autopsied material, the time courses of the degradation of pancreatic insulin, glucagon and hPP were studied using surgically operated pancreatic pieces kept at room or low temperature. Amounts of insulin, glucagon and hPP in pancreatic tissue were determined by radioimmunoassay. Insulin in the pancreas just after resection was 2.58 +/- 0.33 U/g (mean +/- SE). At 3 hrs it decreased to 66.4 +/- 3.8%, at 6 hrs, to 68.5 +/- 5.1% and at 12 hrs to 51.7 +/- 11.4% of the initial value in the tissues kept at room temperature (20-22 degrees C) When the tissues were kept at 4 degrees C, 90.7 +/- 3.9% of insulin at 3 hrs, 88.5 +/- 7.0% at 6 hrs, and 80.3 +/- 2.6% at 12 hrs were preserved. 81.3 +/- 13.9% of the initial hPP was present in the tissues after 6 hrs at room temperature, and it decreased to 20.7 +/- 5.7% after 12 hrs, whereas no significant decrease in hPP was found even after 12 hrs at low temperature. Glucagon content at starting point was 16.85 +/- 4.05 micrograms/g and at 3 hrs in the room temperature it fell to 7.46 +/- 3.53 micrograms/g (41.5 +/- 9.8%) and at 6 and 12 hrs only 14.4 +/- 4.1% and 5.8 +/- 4.2% were left, respectively. At low temperature, at 3 hrs 79.3 +/- 8.9%, at 6 hrs 62.2 +/- 14.7% and at 12 hrs 53.5 +/- 16.6% was preserved. These findings indicate that special consideration should be taken from the viewpoint of the destruction of hormones in pancreatic tissues obtained at autopsy.