Lalita Noronha-Blob

NPC 15669, an inhibitor of neutrophil recruitment, is efficacious in acetic acid-induced colitis in rats

BACKGROUND The efficacy of the leukocyte recruitment inhibitor, N-[9H-2,7-dimethylfluoren-9-ylmethoxy)carbonyl]-L-leucine (NPC 15669) was compared with drugs used to treat inflammatory bowel diseases in a rat model, acetic acid-induced colitis. METHODS Colonic damage assessed by visual inspection, histological quantitation of tissue injury, vascular permeability, myeloperoxidase (MPO) accumulation, and synthesis of inflammatory mediators were measured. RESULTS Intrarectal pretreatment with NPC 15669 results in a significant reduction of all measured indices of inflammation. The median effective dose (ED50) of NPC 15669 for inhibition of MPO accumulation and vascular permeability is 13.2 mg/kg and 31 mg/kg, respectively. The active moiety of sulfasalazine, 5-aminosalicylic acid (5-ASA), the antioxidant/5-lipoxygenase inhibitor, nordihydroguaiaretic acid (NDGA) and the corticosteroids dexamethasone and hydrocortisone, yielded ED50 values (MPO accumulation) of 68 mg/kg, 95 mg/kg, 0.7 mg/kg, and 13 mg/kg, respectively. When formulated suspensions of NPC 15669, 5-ASA, or dexamethasone were used, potency was increased 10-40-fold. Furthermore, NPC 15669 (10 mg/kg) administered 7 hours after acetic acid and evaluated 24 hours after acetic acid administration significantly attenuated neutrophil influx (70% inhibition of MPO accumulation), whereas 5-ASA (100 mg/kg) displayed no therapeutic effects. CONCLUSIONS NPC 15669 may be useful in the treatment of inflammatory disorders.

NPC 15669 enhances survival and reverses leukopenia in endotoxin-treated mice

We now report on the effects of NPC 15669 to reverse endotoxin-mediated leukopenia and to reduce mortality from endotoxic shock in the conscious mouse

Phosphate uptake by kidney epithelial (LLC-PK1) cells

Phosphate uptake by the cultured kidney epithelial cell (LLC-PK1) was studied. The uptake was Na+ dependent, saturable with respect to phosphate and Na+, and energy dependent. The characteristics of the cell uptake system resembled the properties of phosphate transport in the kidney. Parathyroid hormone, dibutyryl cyclic AMP, and forskolin decreased Na+-dependent phosphate uptake. These agonists did not affect Na+-dependent alpha-methylglucoside uptake. Vasopressin and isoproterenol, which do not affect renal phosphate transport, did not inhibit phosphate uptake by the cell. These findings suggest that the cultured cell system may be a useful experimental model for studies of renal phosphate transport and its regulation.

(±)-Terodiline; an Mi-selective muscarinic receptor antagonist. In vivo effects at muscarinic receptors mediating urinary bladder contraction, mydriasis and salivary secretion

The affinity and selectivity of racemic terodiline (N-tert-butyl-1-methyl-3,3-diphenylpropylamine HCl) for muscarinic receptor subtypes was determined from functional responses of rabbit vas deferens (M1), guinea pig atria (M2) and bladder detrusor muscle (M3). (+/-)-Terodiline was found to be about as potent as pirenzepine in the rabbit vas deferens (Kb = 15 and 31 nM, respectively) and at least as selective for M1 relative to M2 (11-fold) and M3 (19-fold) receptors. Like pirenzepine, (+/-)-terodiline does not distinguish between M2 and M3 receptors in vitro. The peripheral actions of (+/-)-terodiline were evaluated in vivo in terms of its ability to induce mydriasis, and to inhibit salivary secretion and urinary bladder contraction. (+/-)-Terodiline given s.c. was equipotent in inhibiting intravesical bladder pressure and carbachol-induced salivary secretion (ID50 = 24 and 35 mg/kg, respectively), and in increasing pupil diameter (ED50 = 59 mg/kg). These results suggest that the in vivo actions of racemic terodiline at (M3) receptors mediating bladder contraction may not be separable from its actions at receptors mediating mydriasis and salivation. Moreover, its effects on the pupil and salivary glands are apparently not mediated through M1 receptors. Together, these findings help clarify the action of (+/-)-terodiline in the treatment of neurogenic bladder.

EFFECT OF EXTRACELLULAR CA2+ ON CHOLINERGIC, KCL AND PHORBOL ESTER-MEDIATED PHOSPHOINOSITIDE TURNOVER AND GUINEA PIG URINARY BLADDER CONTRACTION

The effect of extracellular Ca2+ ([Ca2+]o) on cholinergic, KCl and phorbol ester-mediated detrusor contractions was related to phosphoinositide (PI) breakdown in guinea pig urinary bladder. Carbachol (1.0 mM) elicited a 20-fold increase in inositol phosphate (IP) accumulation both in presence and absence of [Ca2+]o yielding the same EC50 value (approximately 12 microM). In contrast, carbachol-induced detrusor contractions were reduced by 35% without [Ca2+]o, but maximal efficacy was restored with Ca2+ replenishment. In absence of [Ca2+]o, repeated cholinergic stimulation yielded contractions only if tissues were intermittently equilibrated in [Ca2+]o. High K+ and PDBu evoked [Ca2+]o-dependent contractions. Ca2+ channel antagonists and divalent metal cations inhibited high K+ more potently than carbachol-mediated contractions. Together, these findings suggest multiple sources of Ca2+ for urinary bladder contraction, where voltage-sensitive responses depend primarily on [Ca2+]o and PI-linked muscarinic responses involved Ca2+ mobilization from intracellular stores as well. Clinical agents used for the treatment of urinary incontinence inhibited both carbachol-induced PI turnover and muscle contraction with the same rank order of potency both in presence and absence of [Ca2+]o. These findings suggest that the cholinergic mechanism of action of these agents involves the PI-Ca2+ effector system.

Stereoselective antimuscarinic effects of 3-quinuclidinyl atrolactate and 3-quinuclidinyl xanthene-9-carboxylate.

The relative affinity and selectivity of the stereoisomers of 3-quinuclidinyl atrolactate (QNA) and the enantiomers of 3-quinuclidinyl xanthene-9-carboxylate (QNX) for the pharmacologically defined muscarinic receptor subtypes was determined using functional responses of rabbit vas deferens (M1), guinea pig atria (M2) and bladder detrusor muscle (M3). All the stereoisomers behaved as competitive antagonists yielding the same rank order of potency at each receptor subtype: (RR)-QNA greater than (RS)-QNA greater than (SR)-QNA greater than (SS)-QNA and (R)-QNX greater than (S)-QNX. Moreover, the eudismic ratios relative to (RR)-QNA for (RS)-, (SR)- and (SS)-QNA, respectively, ranged from 4 to 308 at all three subtypes. Stereoselective effects were also observed for QNX; (S)-QNX/(R)-QNX ratios ranged from 76 to 248. In contrast, there was a distinct lack of receptor selectivity among the isomers of QNA and QNX for either the M1, M2 or M3 muscarinic receptor subtypes. Stereoselective effects were also evident in vivo in the guinea pig cystometrogram, where the rank order of potency of the isomers of QNA and QNX was similar to that observed in vitro. (RR)-QNA and (R)-QNX equipotently depressed intravesical bladder pressure (PvesP) (ID50 = 0.06 mg/kg i.v.). Other parameters (bladder capacity, threshold pressure) were unaltered by the stereoisomers. The data demonstrate that despite the high affinity of the eutomers of QNA and QNX for muscarinic receptors, they discriminate poorly among muscarinic subpopulations, thus limiting their utility to subclassify muscarinic receptors.

Probe for polyanionic regions on the cell surface

SummaryThe binding of polyuridylate to cells in the presence of proflavine may be used as a probe to provide relative estimates of exposed polyanionic regions on the external surface of the cell. This probe binds preferably to hydrophilic, polyanionic regions, and soluble polysaccharides containing either carboxylate or sulfate groups compete with the binding of this probe. Binding of the probe to protein and lipid regions is considerably weaker. Virustransformed human fibroblasts bind 10 times less of the probe than nontransformed cells when confluent monolayers are compared. However, as the cell density is decreased, the amount of probe bound per cell increases dramatically both for transformed as well as for normal cells. In fact, human fibroblasts (a) derived from normal donors, (b) from donors with different metabolic disorders, and (c) transformed by simian virus 40, all bind about the same amount of probe when compared at the same density. Populations of human fibroblasts aged in vitro, which contain high proportions of large cells and grow only to relatively low densities in monolayers, bind disproportionately large amounts of the complex.