AIMTo study the protection of casein and protamine against degradation of insulin (INS) by proteolysis enzymes and the effect of these two kinds of protein on the hypoglycemic action of INS solution and enteric-microspheres after administrated orally to rats.

METHODSHPLC was used to determine the remained INS in the solution of alpha-chymotrypsin and trypsin with or without casein or protamine; INS solution and enteric-microspheres were prepared and adiministrated orally to rats together with the absorption enhancer sodium N-[8-(2-hydroxybenzoyl) amino] caprylate (SNAC). At the same time, casein or protamine or both of these two kinds of protein were administrated together in order to study their influence on the hypoglycemic effect of INS and microspheres.

RESULTSCasein had a good protection against degradation of INS by alpha-chymotrypsin, but protamine had no protection effect. However, the degradation of INS by trypsin is concerned, the protection effect of protamine on INS was better that of casein. Both of protamine and casein can increase the hypoglycemic effect of INS solution and enteric-microspheres. Co-administrated these two kinds of protein had a better effect. In addition, co-administrated with SNAC, casein and protamine, INS enteric-microspheres had a longer and more potent hypoglycemic effect than that of the solution.

CONCLUSIONCasein and protamine can increase the stability of INS in the intestinal fluid by the mechanism of competition and combine with proteolysis enzymes, which will benefit to INS oral administration.

Administration, Oral ; Animals ; Blood Glucose ; metabolism ; Caprylates ; Caseins ; pharmacology ; Chymotrypsin ; antagonists & inhibitors ; Drug Delivery Systems ; Hypoglycemic Agents ; administration & dosage ; pharmacokinetics ; Insulin ; administration & dosage ; pharmacokinetics ; Male ; Microspheres ; Protamines ; pharmacology ; Rats ; Rats, Sprague-Dawley ; Solutions ; Trypsin ; pharmacology

Metabolic acidosis is a cause of renal disease progression, and alkali therapy ameliorates its progression. However, there are few reports on the role of renal acid-base transporters during alkali therapy. We evaluated the effect of sodium bicarbonate therapy and the role of acid-base transporters on renal disease progression in rats with a remnant kidney. Sprague-Dawley rats consumed dietary sodium bicarbonate (NaHCO3) or sodium chloride (NaCl) with 20% casein after a 5/6 nephrectomy. After being provided with a casein diet, the NaHCO3-treated group had higher levels of serum bicarbonate than the control group. At week 4, the glomerular filtration rate in the NaHCO3 group was higher than that in the NaCl group, and the difference became prominent at week 10. The glomerulosclerosis and tubulointerstitial damage indices in the NaHCO3 group were less severe compared with controls at week 4 and 10. The expression of the Na/H exchanger (NHE) was decreased, and apical reactivity was decreased in the NaHCO3 group, compared with the NaCl group. Endothelin-1 levels in the kidney were also decreased in the NaHCO3 group. Dietary sodium bicarbonate has the effects of ameliorating renal disease progression, which may be related to the altered expression of NHE in the remaining kidney.
Acidosis/*drug therapy ; Alkalies/*therapeutic use ; Animals ; Caseins/administration & dosage ; Disease Progression ; Glomerular Filtration Rate/drug effects ; Glomerulosclerosis, Focal Segmental/drug therapy ; Kidney/injuries ; Male ; Nephrectomy ; Nephritis, Interstitial/drug therapy ; Rats ; Rats, Sprague-Dawley ; Renal Insufficiency/*drug therapy ; Sodium Bicarbonate/*therapeutic use ; Sodium Chloride/administration & dosage ; Sodium-Hydrogen Antiporter/*antagonists & inhibitors