Ivens A. Siegel

Surfactant-induced increases of permeability of rat oral mucosa to non-electrolytes in vivo

The effect of non-ionic, cationic and anionic surfactants on non-electrolyte permeability of rat oral mucosa in vivo was tested. The surfactants caused an increase in mucosal permeability to oil-soluble compounds and small and large water-soluble compounds. The effect was concentration-dependent, and both the cationic and anionic surfactants were more potent than the non-ionic compounds. Surfactant-treated tissue showed widening of the stratum corneum due to separation of layers and loss of surface layers. Measurement of the permeability to sodium lauryl sulphate indicated that this anionic surfactant produced damage to the permeability barrier.

Mechanisms of non-electrolyte penetration across dog and rabbit oral mucosa in vitro

Abstract Permeability coefficients were determined for 20 14 C-labelled compounds using canine and rabbit lingual frenulum as the test tissue. The oil-to-water distribution coefficients of these compounds differed by over 5 × 10 5 -fold. A linear relationship between permeability coefficients and oil-to-water distribution coefficients was found for those compounds with oil-to-water distribution coefficient greater than that of water, demonstrating the importance of lipid solubility on the rate of transfer across oral mucosa. The data further indicate that hydrogen bonding, cylindrical radius and chemical differences contribute to penetration rates. The plot of permeability coefficient versus molecular volume for compounds with oil-to-water distribution coefficients less than that of water is biphasic, suggesting two different routes of permeation for these compounds. This indicates that oil-soluble compounds traverse oral mucosa via solvation, whereas water-soluble molecules with a molecular volume of less than 80 cm 3 /mol cross primarily through membrane pores; larger water-soluble molecules pass extracellularly.

Aequorin: Its ionic specificity

Abstract The specificity of the cation-aequorin luminescent reaction was investigated. Contrary to present belief, this reaction was not specific for Ca 2+ and Sr 2+ . Over a dozen cations were capable of eliciting light emission from aequorin. Although these cations are not normally present in significant amounts in biological fluids, the present observations may be of importance in interpretting the luminescence obtained after the intracellular injection of aequorin.

Surfactant-induced alterations of permeability of rabbit oral mucosa in vitro.

The permeability of rabbit oral mucosa to eight nonelectrolytes was measured in vitro in the absence and in the presence of 0.025, 0.1, and 1.0% concentrations of anionic, cationic, and nonionic surfactants. The anionic surfactant sodium lauryl sulfate and the cationic surfactants cetyltrimethylammonium bromide and cetylpyridinium chloride caused greater increases in permeability than polysorbate 80, a nonionic surfactant. The increases in permeability brought about by the surfactants were concentration dependent.

A microsomal HCO3−-stimulated ATPase from the dog submandibular gland

A HCO3−-stimulated, Mg2+-dependent ATPase (ATP phosphohydrolase, EC 3.6.1.3) present in a microsomal fraction prepared from dog submandibular glands was investigated. The bicarbonate concentration necessary for half maximal activation of the enzyme was about 2 mM and the optimum pH was 7.7. The enzyme was completely inhibited by SCN− but only partially inhibited by ouabain or acetazolamide. The HCO3−-stimulated ATPase activity was correlated with dinitrophenol stimulation and with succinate dehydrogenase activity. This suggests that the enzyme is of mitochondrial origin.

Bicarbonate ion-ATPase in rat liver cell fractions

The distribution of HCO3MINUS-ATPase activity was studied in cell fractions prepared from homogenates of rat liver. The level of mitochondrial contamination in the microsomal fraction depended on the fractionation procedure and on the method of homogenization. With proper care, microsomes with undetectable mitochondrial contamination could be prepared. These microsomes had no detectable HCO3MINUS-ATPase activity. Approximately 85% of the total HCO3minus-ATPase activity of the post 6000 times g-min supernatant was recovered in the mitochondrial fraction. The properties of this mitochondrial HCO3minus-ATPase were not distinguishable from those of the various microsomal HCO3minus-ATPases previously described by other investigators.

Calcium-stimulated ATPase of dog submandibular gland

Abstract A Ca 2− -stimulated ATPase present in a microsomal fraction prepared from canine submandibular glands was investigated. The Ca 2+ concentration for half maximal activation of the enzyme was about 0.3 mM. Addition of Mg 2+ to incubation media containing Ca 2+ decreased the ATPase activity. The presence of neither Na + nor K + is required for Ca 2+ -activation of the enzyme. Also, Ca 2+ will not substitute for Mg 2+ in the Mg 2+ -dependent (Na + + K + )-ATPase reaction. The Ca 2+ -activation was not appreciably affected by ouabain (10 −4 M), but was inhibited by about 50 per cent by 5 × 10 −3 M ethacrynic acid. These studies provide a possible enzymatic basis for the calcium uptake by salivary gland microsomes that has been reported by other workers.

Permeability of the rat oral mucosa to organic solutes measured in vivo

The permeability of the oral mucosa to organic solutes of different molecular volumes, oil-to-water distribution coefficients, and pKa was studied in an in-vivo system. The calculated permeability coefficients were independent of time of application and the concentration of the solutes, a finding consistent with transport by simple diffusion. The permeability of organic acids was pH dependent whereas permeability to compounds with a degree of ionization that did not change over the pH range was not affected by pH. Increasing the chain length from two to eight carbons in an organic acid series resulted in an increase of both the oil-to-water distribution coefficient and the permeability coefficient; the permeability coefficient was decreased by the addition of oxygen in the form of hydroxyl groups. These results indicate that there is similarity in the way that lipid-soluble substances diffuse across oral mucosa and other lipid membranes. Results using compounds with oil-to-water distribution coefficients less than that of water suggest that these compounds traverse the oral mucosa by two additional routes. One, for compounds with molar volumes less than 80 cm3/ml, is via pores; whereas, the second, utilized by larger compounds, is probably by an intercellular route.

Permeability of Oral Mucosa to Organic Compounds

It is generally considered that substances possessing high lipid solubility penetrate mucosa more rapidly than substances with low lipid solubility (Brodie and Hogben, J Pharm Pharmcol 9:345, 1957). Our present experiments were designed to both examine the validity of this hypothesis by determining the permeability constants (Kp) of oral mucosal tissue to organic molecules with differing lipid to water solubility ratios and to compare tissue from different areas of the oral cavity. Attached gingiva from upper incisors and the lingual frenulum were removed from adult male New Zealand rabbits anesthetized with sodium pentobarbital. The frena were split, exposing an oral side and a blood side. Both frena and gingiva were placed in oxygenated Krebs-Ringer phosphate (KRP) solution and cleaned free of extraneous tissue. The resulting thin tissues were mounted in lucite chambers (Ussing, Acta Physiol Scand 17:1, 1949). Both half-chambers were filled with KRP, and an isotope of the compound being tested was added to the half-chambers facing the oral side of the tissue. Tenpl aliquots were removed from both half-chambers at 30-minute intervals and counted using conventional liquid scintillation counting techniques. The Kp values were calculated using the Fick formula as described by Siegel et at (JPharm Sci 65:129, 1976):

Rat parotid gland pathophysiology following 137Cs irradiation.

Changes in rat parotid gland function were measured between 3 and 30 days following exposure to 1800 R of137 Cs irradiation to the head. Glandular fluid secretion capability as indicated by volume of secretion, maximum rate of secretion, and duration of secretion following pilocarpine stimulation decreased concomitantly with gland weight following irradiation. Thus gland weight is probably indicative of residual glandular potential for fluid secretion following irradiation. The relation between salivary sodium concentration and flow rate was assumed to be indicative of glandular electrolyte transport capability. Salivary sodium concentrations were not elevated over control values at any flow rate. Therefore, there is no evidence for an irradiation-induced defect in the ductal sodium resorption mechanism. Rather, the observed salivary sodium changes are consistent with a decrease in the relative glandular proportion of acini to ducts.