Ways of utilizing the true separation efficiency of monolithic silica (MS) columns were studied. The true performance of MS columns, both regular-sized (rod-type clad with PEEK resin, 4.6 mm ID, 10 cm) and capillary sized (in 100 or 200 microm ID fused silica capillary, 25-140 cm) was evaluated by calculating the contribution of extra-column effects. HETP values of 7-9 microm were observed for solutes having retention factors (kvalues) of up to 4 for rod columns and up to 15 for a capillary column. The high permeability of MS columns allowed the use of long columns, with several connected together in the case of rod columns. Narrow-bore connectors gave good results. Peak variance caused by a column connector ranges from 50 to 70% of that caused by one rod-type column for up to three connectors or four columns in 80% methanol, but the addition of a 4th or 5th connector to add a 5th and 6th column, respectively, caused a much greater increase in peak variance, especially for long-retained solutes, which is greater than the variance caused by one rod column. Rod columns seem to show slightly lower efficiency at a pressure higher than 10 MPa or so. The use of acetonitrile-water as a mobile phase better preserved the ability of individual rod columns to generate up to 100,000 theoretical plates with 14 columns connected. Methods for eliminating extra-column effects in micro-HPLC were also studied. Split injection and on-column detection resulted in optimum performance. A long MS capillary measuring 140 cm produced 160,000 theoretical plates. The column efficiency of a capillary column was not affected by the pressure, showing advantages over the rod columns that exhibited peak broadening caused by connectors and pressure.

PPARγ-agonists enhance insulin sensitivity and improve glucose utilization in diabetic patients. Adverse effects of PPARγ-agonists include volume retention and edema formation. Recent observations pointed to the ability of PPARγ agonists to enhance transcription of the serum and glucocorticoid-inducible kinase SGK1, a kinase that is genomically upregulated by mineralocorticoids and stimulates various renal channels and transporters including the renal epithelial Na + channel ENaC. SGK1 has been proposed to mediate the volume retention after treatment with PPARγ agonists. To test this hypothesis, food containing the PPARγ agonist pioglitazone (0.02%, i.e., approximately 25 mg/kg bw/day) was administered to gene-targeted mice lacking SGK1 (sgk1 −/− , n=12) and their wild-type littermates (sgk1 +/+ , n=12). According to in situ hybridization, quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) and immunofluorescence, treatment with pioglitazone significantly increased renal SGK1 mRNA and protein expression in sgk1 +/+ mice. The treatment increased body weight significantly in both, sgk1 +/+ mice (+2.2±0.3 g) and sgk −/− mice (+1.3±0.2 g), and decreased hematocrit significantly in sgk1 +/+ mice (−6.5±1.0%) and sgk1 −/− mice (−3.1±0.6%). Both effects were significantly (p<0.05) more pronounced in sgk1 +/+ mice. According to Evans Blue

PPARγ agonists, such as pioglitazone, are widely used in the treatment of diabetes and several further disorders. They enhance transcription of the serum and glucocorticoid inducible kinase SGK1, which could in turn enhance gastric acid secretion by stimulating KCNQ1 K⁺ channels. The present study explored whether pioglitazone upregulates SGK1 protein expression in gastric glands and thus modifies gastric acid secretion. Food containing the PPARγ agonist pioglitazone (approximately 25mg/kg bw/day) was administered to gene-targeted mice lacking SGK1 (sgk1^-/-, n=11) and their wild-type littermates (sgk1^+/+, n=11). Western blotting was employed to analyze SGK1 expression, BCECF-fluorescence to determine acid secretion in isolated gastric glands and immunohistochemistry to elucidate KCNQ1 and H⁺/K⁺-ATPase protein abundance in the parietal cell membrane. Pioglitazone significantly increased SGK1 expression. Cytosolic pH and cellular buffer capacity were not significantly different between sgk1^+/+and sgk1^-/- mice and not significantly modified in either genotype by pioglitazone. Without pioglitazone treatment, Na⁺-independent pH-recovery following an ammonium pulse (ΔpH/min) reflecting H⁺/K⁺-ATPase activity was again similar in sgk1^+/+and sgk1^-/- mice. Pioglitazone significantly increased ΔpH/min (≈3 fold) in sgk1^+/+ but not in sgk1^-/- mice. H⁺/K⁺-ATPase inhibitor omeprazole (100 μM) abolished ΔpH/min in both genotypes irrespective of pioglitazone treatment. Increase in local K⁺ concentrations to 35 mM (replacing Na⁺/NMDG) significantly increased ΔpH/min and abrogated the differences between genotypes. KCNQ1 and H⁺/K⁺-ATPase protein abundance in the parietal cell membrane was enhanced by pioglitazone treatment in sgk1^+/+but not in sgk1^-/- mice. In conclusion, pioglitazone increases gastric acid secretion, an effect at least partially due to stimulation of SGK1 expression and SGK1-dependent upregulation of KCNQ1.