Renal V2 vasopressin receptor proteins: identification and enrichment.

The synthesis of the tritium labelled photoreactive analogue of 1-deamino-vasopressin [1-(3-mercaptopropionic acid, 8-(N6-4-azido-phenylamidino)-lysine] vasopressin is described. This analogue retains a high affinity for hepatic V1 and renal V2 vasopressin receptors (apparent dissociation constant KD approximately 1-2 nM). A membrane protein from bovine kidney and pig kidney with an apparent relative molecular mass (Mr) of 30,000 was preferentially labelled and with lower yield a protein band with a Mr-value of 50,000 to 60,000. The photolabelled 30,000-Mr protein from bovine kidney was enriched by size-exclusion chromatography and by reversed-phase-high-performance liquid chromatography.

Comparative study of fosfomycin activity in Mueller-Hinton media and in tissues.

Fosfomycin utilizes two uptake systems as ways of entry into microorganisms: the L-a-glycerophosphate and the hexose phosphate transport system. The latter is inducible by glucose-6-phosphate. The relationship between glucose-6-phosphate (concentration range 0-100 mg/l) and the susceptibility of Staphylococcus aureus was studied in Mueller-Hinton broth. An almost maximal enhancement of fosfomycin activity was found at 25 mg/l glucose-6-phosphate. Fosfomycin activity against Staph. aureus, Escherichia coli, Proteus mirabilis, Enterobacter cloacae, Klebsiella spp., Serratia spp., and Pseudomonas aeruginosa was studied by use of the broth and the agar dilution method, in the presence and absence of glucose-6-phosphate (25 mg/l). The minimum inhibitory concentrations (MICs) of fosfomycin against Staph. aureus Streptococcus faecalis, E. coli, Ent. cloacae, Pr. mirabilis, and Ps. aeruginosa were estimated in particle free supernatants of 25% tissue homogenates (liver, kidney, lung, heart) and in parallel in Mueller-Hinton broth. With few exceptions the MICs in Mueller-Hinton broth (with glucose-6-phosphate) were similar to those found in tissues (no glucose-6-phosphate added).