Yuji Kurosaki

Prediction of the Plasma Concentration Profiles of Orally Administered Drugs in Rats on the Basis of Gastrointestinal Transit Kinetics and Absorbability

A new method based on gastrointestinal transit kinetics has been developed for estimation of the absorption profiles of drugs administered orally as aqueous solutions. The utility of the method was evaluated in rats.

Beliefs of chronically ill Japanese patients that lead to intentional non-adherence to medication

Objective:  To identify factors, associated with personal beliefs, involved in intentional non‐adherence to prescribed medication of Japanese patients with chronic diseases.

Endogenous calcitonin gene-related peptide (CGRP) mediates adrenergic-dependent vasodilation induced by nicotine in mesenteric resistance arteries of the rat

The mechanisms underlying vasodilator effect of nicotine on mesenteric resistance blood vessels and the role of calcitonin gene‐related peptide (CGRP)‐containing (CGRPergic) vasodilator nerves were studied in the rat. Mesenteric vascular beds isolated from Wistar rats were perfused with Krebs solution, and perfusion pressure was measured with a pressure transducer. In preparations with intact endothelium and contracted by perfusion with Krebs solution containing methoxamine, perfusion of nicotine (1–100 μM) for 1 min caused a concentration‐dependent vasodilator response without vasoconstriction. The nicotine‐induced vasodilation was markedly inhibited by hexamethonium (nicotinic cholinoceptor antagonist, 10 μM) and blocked by guanethidine (adrenergic neuron blocker, 5 μM). Either denervation by cold storage (4°C for 72 h) or adrenergic denervation by 6‐hydroxydopamine (toxin for adrenergic neurons, 2 mM for 20 min incubation, twice) blocked the nicotine‐induced vasodilation. Neither endothelium removal with perfusion of sodium deoxycholate (1.80 mg ml−1, for 30 s) nor treatment with Nω‐nitro‐L‐arginine (nitric oxide synthase inhibitor, 100 μM), atropine (muscarinic cholinoceptor antagonist, 10 nM) or propranolol (β‐adrenoceptor antagonist, 100 nM) affected the nicotine‐induced vasodilation. In preparations without endothelium, treatment with capsaicin (depleting CGRP‐containing sensory nerves, 1 μM) or human CGRP[8–37] (CGRP receptor antagonist, 0.5 μM) markedly inhibited the nicotine‐induced vasodilation. These results suggest that, in the mesenteric resistance artery of the rat, nicotine induces vasodilation, which is independent of the function of the endothelium and is involved in activation of CGRPergic nerves. It is also suggested that nicotine stimulates presynaptic nicotinic cholinoceptors on adrenergic nerves to release adrenergic neurotransmitters, which then act on CGRPergic nerves to release endogenous CGRP from the nerve.

Enhancing effect of 1-dodecylazacycloheptan-2-one (Azone) on the absorption of salicylic acid from keratinized oral mucosa and the duration of enhancement in vivo

Abstract Enhancing effect of the pretreatment with 1-dodecylazacycloheptan-2-one (Azone) on the absorption of salicylic acid from keratinized oral mucosa was investigated in vivo using a hamster cheek pouch. The absorption was significantly increased after the 4 h pretreatment with Azone-emulsion when the pretreatment medium contained Azone above 0.2%. The enhancement was observed at all pH conditions examined irrespective of the degree of dissociation of the drug. The apparent disappearance rate constant of salicylic acid, calculated from the time course of the sum of remaining amounts of the drug in both the luminal fluid and the tissue, in Azone-pretreated cheek pouch was approximately 2.7 times larger than in the non-treated one. The pharmacokinetic analysis of the plasma concentration of salicylic acid after the intra-cheek-pouch administration revealed that Azone pretreatment enhanced the absorption i.e., increased the absorption rate constant and shortened the mean absorption time by one-fifth, and brought the peak plasma concentration approximately twice higher. The enhanced absorption after 1 h pretreatment with 5% Azone-emulsion diminished with the lapse of time and the barrier function of the cheek pouch was completely recovered within 6 h after the removal of the Azone-emulsion.

Regional Variation in Oral Mucosal Drug Absorption: Permeability and Degree of Keratinization in Hamster Oral Cavity

The regional permeability of oral mucosa to salicylic acid was investigated in vivo in hamsters along with histological variations, especially the degree of keratinization. Histological sections from six regions, i.e., sublingual mucosa, buccal mucosa, dorsum of tongue, ventral surface of tongue, labial mucosa, and cheek pouch mucosa, were prepared to assess the degree of keratinization. The area under the plasma concentration–time curve of salicylic acid following the administration of salicylic acid to the oral mucosa with a film dosage form and the thickness of stratum corneum of each site were in inverse proportion to each other, suggesting that the stratum corneum layer represents the principle barrier to drug absorption.

Long-Term Inhibition of Angiotensin Prevents Reduction of Periarterial Innervation of Calcitonin Gene-Related Peptide (CGRP)-Containing Nerves in Spontaneously Hypertensive Rats

The aim of this study was to investigate age-related changes in the density of calcitonin gene-related peptide (CGRP)-containing nerve fibers in spontaneously hypertensive rats (SHR) and the effects of long-term inhibition of the renin-angiotensin system on these changes. The density of immunocytochemically stained nerve fibers in the mesenteric artery was quantified by computer-assisted image processing. An age-related decrease in the density of CGRP-like immunoreactive (LI)-containing nerve fivers but not neuropeptide Y (NPY)-LI-containing sympathetic nerve fibers was found in the mesenteric artery of SHR but not Wistar Kyoto rats (WKY). The density of NPY-LI-containing sympathetic nerve fibers was significantly greater in SHR than in WKY. SHR were treated for 7 weeks with angiotensin converting enzyme inhibitor (0.005% temocapril), angiotensin II type-1 (AT1) receptor antagonist (0.025% losartan) or vasodilator (0.01% hydralazine) in their drinking water. Each drug treatment significantly lowered the systolic blood pressure measured by tail-cuff method. Long-term treatment of SHR with temocapril and losartan significantly increased the density of CGRP-LI-containing nerve fibers in mesenteric arteries. However, the density after hydralazine treatment was similar to the level in non-treated SHR. The density of NPY-LI-containing nerve fibers was not increased by any of the drug treatments. These results suggest that long-term inhibition of the renin-angiotensin system in SHR prevents remodeling of CGRPergic nerve fibers and prevents the reduction of CGRPergic nerve function.

Effects of surfactants on the absorption of salicylic acid from hamster cheek pouch as a model of keratinized oral mucosa

Abstract The effect of surfactants on the absorption of salicylic acid from keratinized oral mucosa was investigated by hamster cheek pouch method in vivo at pHs 3.0, 4.0 and 7.0. Four surfactants, sodium laurylsulfate (SLS), cetylpyridinium chloride (CPC), polysorbate 80 (PS-80) and sodium taurocholate (STC), were examined as adjuvants. The interaction between salicylic acid and each surfactant was determined by the molecular sieve method using Sephadex G-25. Decreased absorption of salicylic acid by the presence of PS-80 was observed in the lower pH conditions and this phenomenon was explained by the decrease in the free fraction of salicylic acid. The absorption of salicylic acid in the presence of ionic surfactants, SLS or CPC, was much larger than that predicted by the loss of activities which was caused by the interaction between the surfactant and the drug molecule. Pretreatment with SLC or CPC brought the salicylic acid absorption to increase in all pH conditions examined and the effects were dependent on the surfactant concentration. STC and no effect on the absorption. The mechanisms of the effects of ionic surfactants on the permeability of keratinized oral mucosa were discussed.

Use of lipid disperse systems in transdermal drug delivery: Comparative study of flufenamic acid permeation among rat abdominal skin, silicon rubber membrane and stratum corneum sheet isolated from hamster cheek pouch

Abstract The characteristics of in vitro permeation of flufenamic acid (FA) from lipid disperse systems composed of phosphatidylcholine (PC) and glycosylceramide (GC) were compared among rat abdominal skin, a silicon rubber membrane (Silastic ® ) and a stratum corneum (SC) sheet isolated from hamster cheek pouch. When a PC dispersion (PCD) containing 20 μmol PC/ml was applied, the permeation of FA through rat skin was enhanced approx. 2.2-fold compared with that from the lipid-free suspension (LFS). Further, a nearly 2-fold enhancement was observed when a GC-containing PCD (10% GC-PCD) was examined. A similar pattern of enhancement could be reproduced when cheek pouch SC was used instead of, rat skin, whereas it was not observed in Silastic ® . The enhanced permeation in the skin could not be explained on the basis of the incremental increase in the apparent solubilities. A significant correlation was observed between skin permeation and epidermal tissue uptake of FA from LFS and PCDs, although the nearly 2-fold increase found in 10% GC-PCD might be due to mechanisms other than the increase in epidermal tissue uptake. The usefulness of an SC sheet isolated from hamster cheek pouch, a new model membrane without appendages, in studying the direct action of either permeation enhancers or dosage forms designed to enhance the percutaneous permeation of drugs on the SC is discussed.

Vanilloid receptors mediate adrenergic nerve- and CGRP-containing nerve-dependent vasodilation induced by nicotine in rat mesenteric resistance arteries

Previous studies showed that nicotine induces adrenergic nerve‐dependent vasodilation that is mediated by endogenous calcitonin gene‐related peptide (CGRP) released from CGRP‐containing (CGRPergic) nerves. The mechanisms underlying the nicotine‐induced vasodilation were further studied. Rat mesenteric vascular beds without endothelium were contracted by perfusion with Krebs solution containing methoxamine, and the perfusion pressure was measured with a pressure transducer. Perfusion of nicotine (1–100 μM) for 1 min caused concentration‐dependent vasodilation. Capsazepine (vanilloid receptor‐1 antagonist; 1–10 μM) and ruthenium red (inhibitor of vanilloid response; 1–30 μM) concentration‐dependently inhibited the nicotine‐induced vasodilation without affecting the vasodilator response to exogenous CGRP. Nicotine‐induced vasodilation was not inhibited by treatment with 3,4‐dihydroxyphenylalanine (DOPA) receptor antagonist (L‐DOPA cyclohexyl ester; 0.001–10 μM), dopamine D1 receptor‐selective antagonist (SCH23390; 1–10 μM), dopamine D2 receptor antagonist (haloperidol; 0.1–0.5 μM), ATP P2x receptor‐desensitizing agonist (α,β‐methylene ATP; 1–10 μM), adenosine A2 receptor antagonist (8(p‐sulfophenyl)theophylline; 10–50 μM) or neuropeptide Y (NPY)‐Y1 receptor antagonist (BIBP3226; 0.1–0.5 μM). Immunohistochemical staining of the mesenteric artery showed dense innervation of CGRP‐ and vanilloid receptor‐1‐positive nerves, with both immunostainings appearing in the same neuron. The mesenteric artery was also densely innervated by NPY‐positive nerves. Double immunostainings showed that both NPY and CGRP immunoreactivities appeared in the same neuron of the artery. These results suggest that nicotine acts on presynaptic nicotinic receptors to release adrenergic neurotransmitter(s) or related substance(s), which then stimulate vanilloid receptor‐1 on CGRPergic nerves, resulting in CGRP release and vasodilation.

Chronic hyperinsulinemia enhances adrenergic vasoconstriction and decreases calcitonin gene-related peptide-containing nerve-mediated vasodilation in pithed rats.

The present study investigated the influence of chronic hyperinsulinemia on vascular responsiveness induced by adrenergic nerves and calcitonin gene–related peptide–containing (CGRPergic) nerves in pithed rats with insulin resistance. Male Wistar rats (6 weeks old) received 15% fructose solution in drinking fluid for 10 weeks (fructose-drinking rats: FDR), which resulted in significant increases in plasma levels of insulin, total cholesterol and triglyceride, and systolic blood pressure, as compared with control rats. Pithed FDR showed greater adrenergic nerve–mediated pressor response to spinal cord stimulation (SCS) at the lower thoracic vertebra (Th 9–12) and pressor response to exogenous noradrenaline than control rats. In pithed FDR with blood pressure artificially increased by continuous infusion of methoxamine and blockade of autonomic ganglia by hexamethonium, CGRPergic nerve–mediated depressor responses to SCS were significantly smaller than those in control rats, but depressor responses to other vasodilators such as acetylcholine, CGRP and sodium nitroprusside were similar to those in control rats. These results suggest that chronic hyperinsulinemia in FDR facilitates adrenergic nerve–mediated vasoconstriction, which is associated with attenuated CGRPergic nerve–mediated vasodilation.