The absorption of chondroitin sulphate (CSA) has been investigated in rabbits after the oral administration of a single dose of 100 mg of CSA per kg of body weight. The oral dose was administered as a lipid suspension or in enteric capsules. No absorption of CSA could be demonstrated. Oral administration did not cause the release of a clearing factor into the bloodstream, a phenomenon that is known to occur in the presence of CSA. The concentration of this factor did not decrease after oral administration of CSA.
Inhibition of ciliary process adenylate cyclase was studied on rabbit membrane preparations. When considered individually, epinephrine, GTP and NaCl did not inhibit adenylate cyclase activity. On the other hand, when present together, epinephrine, GTP (10(-5) M) and NaCl (200 mM) acted synergistically to cause a 27% inhibition of basal activity. A similar inhibition was observed with 1-norepinephrine. Clonidine and BHT 920, two alpha 2-agents were found to be partial agonists causing 63% and 82% as much inhibition as epinephrine. Phenylephrine, an alpha 1-agonist did not inhibit adenylate cyclase activity at concentrations up to 10(-4) M. Yohimbine and phentolamine prevented the inhibition of adenylate cyclase by epinephrine, while prazosin was ineffective. Alpha 2-receptor selectivity in rabbit ciliary processes and their negative coupling to an adenylate cyclase via a NaCl-dependent GTP binding protein, Ni, is thus well established.
The synthesis of R-(+) and S-(-) isomers of O-[3-tert-butylamino)-2-hydroxypropyl] cyclopropyl methyl ketone oxime (falintolol) is described. The syn and anti isomers of falintolol were obtained in two different ways from cyclopropyl methyl ketoxime or from falintolol. For comparison purposes, the enantiomers of the dicyclopropyl ketone oxime derivatives were also prepared. Structure-activity relationships are described.
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