The injection of streptozotocin(stz) at a high dose (60 mg/kg) into young male rats produces direct beta cell destruction and leads to insulin dependent diabetes (IDD). In contrast the injection of multiple smal doses of stz (40 mg/Kg/d for 5 days) produce IDD, which resembles type l diabetes in man. The provocative effects of the pertussis vaccine (PV) and cyclosporin(CA) against the development of IDD induced by stz were studied. When PV in a dose of 3.75 X 10(10) microorganism was administered to single or multiple stz treated rats, hyperglycemia still developed and persisted during the experiment. No difference was noted in blood glucose levels, but plasma insulin levels were higher in PV treated rats. When CA (10 mg/kg) was administered daily to single or multiple stz treated rats, hyperglycemia seemed to be lower, but this was not statistically significant, however, plasma insulin levels were higher in CA treated rats. The results of this experiment suggest that PV and CA provide some protection to the beta cells of the pancreas.
Animal ; Blood Glucose/metabolism ; Cyclosporins/pharmacology* ; Diabetes Mellitus, Experimental/prevention & control* ; Diabetes Mellitus, Insulin-Dependent/chemically induced ; Male ; Pertussis Vaccine/pharmacology* ; Rats ; Rats, Inbred Strains

To study the effect of P-glycoprotein (P-gp) on the absorption of buagafuran in ileum, the concentration of buagafuran in Caco-2 cells, rat averted intestinal sacs and recirculating perfusion were determined by UV-HPLC method. Verapamil and cyclospirin A (CsA) were used as P-gp inhibitors. The results showed that the transportation of buagafuran across Caco-2 monolayer showed vectorial manner. The permeation of buagafuran from apical (A) to basolateral (B) side was 11% and 24.8% from B to A side. Verapamil and CsA were found to increase the transport of buagafuran by 1.4 and 1.35 fold from A to B side and decrease by 71% and 75% from B to A side, respectively, compared with control. The uptake of buagafuran in Caco-2 cell was also enhanced by P-gp inhibitors, especially in low concentration of buagafuran. Ninety percent of buagafuran was absorbed after 90 min perfusion. Verapamil and CsA were found to improve the absorption of buagafuran at all time points, especially at 30 min (12.4% and 21.5%, respectively). During the incubation, only 14% of buagafuran left in rat averted intestinal sacs, while buagafuran levels were increased in both intestine homogenate and sacs by adding verapamil and CsA. The results indicated that buagafuran was one of the P-gp substrates based on the present study. The absorption of buagafuran can be blocked by P-gp, resulting in the enhancement of buagafuran metabolism in intestine. The poor bioavailability of buagafuran may be partially due to the effect of P-gp on its absorption and transportation in intestinal lumen.
ATP-Binding Cassette, Sub-Family B, Member 1 ; antagonists & inhibitors ; metabolism ; Animals ; Biological Transport ; Caco-2 Cells ; Cyclosporins ; pharmacology ; Humans ; Intestinal Absorption ; drug effects ; Intestine, Small ; metabolism ; Male ; Rats ; Rats, Sprague-Dawley ; Sesquiterpenes ; pharmacokinetics ; Verapamil ; pharmacology

OBJECTIVETo explore the efficacy of PSC 833 on multidrug resistance (MDR) reversal and its mechanism.

METHODSHuman erythroleukemic cell line K562 and its doxorubicin-resistant counterpart K562/A02 were used in the study. Cytotoxicity was assessed by MTT assay, P-gp expression by direct immunofluorescence and mdr1 mRNA expression by reverse transcriptase polymerase chain reaction (RT-PCR) with beta-actin as internal control. Intracellular DNR retention was measured with flow cytometry.

RESULTSK562/A02 cells displayed high levels of mdr1 mRNA and P-glycoprotein and reduced DNR retention compared to their parental K562 cells. 1 micromol/L of PSC 833 had no effect on the levels of mdr1 mRNA and P-gp expression in K562/A02 cells (P > 0.05). PSC 833 conferred a dose-dependent increase on chemosensitivity of K562/A02 to DNR, and its effect was at least 3-fold more potent than that of CsA or Ver. PSC 833 could increase DNR retention in K562/A02 cells. A 100.9% restoration of intracellular DNR retention of the level of K562 cells was gained by PSC 833 at 1.0 micromol/L in K562/A02 cells, whereas only a 86.9% restoration of DNR retention was obtained by CsA at 10 micromol/L in the K562/A02 cells. No effect on DNR sensitivity and retention was found in K562 cells (P > 0.05).

CONCLUSIONPSC 833 is at least 3 approximately 10 fold more potent than CsA or Ver with respect to MDR reversing activity, and it may function by inhibiting the function of P-gp and not reducing the levels of mdr1 mRNA and P-gp directly.

ATP-Binding Cassette, Sub-Family B, Member 1 ; drug effects ; genetics ; metabolism ; Calcium Channel Blockers ; pharmacology ; Cyclosporine ; pharmacology ; Cyclosporins ; pharmacology ; Dose-Response Relationship, Drug ; Drug Resistance, Neoplasm ; Humans ; K562 Cells ; cytology ; drug effects ; metabolism ; RNA, Messenger ; drug effects ; genetics ; metabolism ; Verapamil ; pharmacology