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The predominant renal and urinary forms of nickel consist of low-Mr complexes. Similarities in the nature of these complexes have been found in kidneys of rats exposed parenterally to NiCl2 and in rat kidneys treated with NiCl2 in vitro. Similar complexes have also been identified after treatment of bovine and human renal soluble fractions with NiCl2. The bulk of nickel in all cases is associated with sulphated oligosaccharide fractions containing uronic acids and neutral sugars. This binding is non-specific, and nickel is readily displaced from these fractions by copper. Smaller amounts of nickel are bound to an acidic peptide, which was purified from human kidneys and partially characterized. Nickel was not displaced from this material by copper at physiological pH. These nickel complexes have not been found in plasma, suggesting that ligand exchange occurs during or after glomerular filtration of the metal.

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The influence of the autonomic nerves on sublingual glands of rats was studied. Stimulation of the chorda-lingual nerve evoked a lively flow of saliva and was also thought to contract the myoepithelial cells in the gland. Sympathetic nerve stimulation, on the other hand, usually evoked no secretion and did not cause any motor responses in the sublingual gland. The glandular blood flow was increased by chorda-lingual nerve stimulation, and this vasodilatation persisted also when atropine had been administered. Sympathetic nerve stimulation decreased the sublingual blood flow; this vasoconstrictor effect was mediated via activation of a-adrenoceptors.Rat salivary glands have been increasingly used to investigate the secretory mechanisms of water, electrolytes and organic substances in exocrine glands in vivo and in vitro [see Ohlin, 1966;Schneyer, Young and Schneyer, 1972;Young, 1973;Selinger, Eimerl, Savion and Schramm, 1974;Thulin, 1976]. The sublingual gland of the rat is considered to be a convenient system for comparative studies of secretion from serous and mucous cells since both cell types are present in the acini of this gland [Kim, Nasjleti and Han, 1972].The innervation pattern of the sublingual gland of the rat is well established morphologically. Thus, the autonomic nerve terminals which are present around the acini seem to be cholinergic and are in very close association with the parenchymal and myoepithelial cells [Snell and Garrett, 1957; Scott and Pease, 1959]. According to Norberg and Olson [1965] adrenergic nerve terminals are found only adjacent to the blood vessels and at a relatively long distance from the parenchymal and the myoepithelial cells, although it has been proposed that the mucous cells of the sublingual acini are sympathetically innervated [Fujiwara, Tanaka, Hattori and Honjo, 1966]. But no information is available concerning the influence of the autonomic nerves on different effector cells in the rat sublingual gland, although secretion elicited by different secretagogues such as methacholine, adrenaline and isoprenaline has been studied in this gland by Ohlin and Perec [1965]. Accordingly secretory and motor events in the sublingual gland resulting from nerve stimulation and the administration of drugs have now been studied. Observations on the glandular blood flow were also made. METHODSForty male Wistar rats (280-380 g), anaesthetized with chloralose (100 mg. kg-') administered via a cannulated femoral vein after induction with ether, were used. A tracheal tube was inserted. The sublingual duct was cannulated either on the right or on the left side with a glass 59

The sensitivity to methacholine of the parotid glands in rats maintained on a liquid diet (aiming at sensitization) for a period of 2 weeks or 3-4 weeks was compared with that of the parotid glands in rats on a pelleted bulk diet (aiming at desensitization). In the rats on the liquid diet, it was found that the dose needed to evoke a just perceptible secretion of saliva was smaller, that the secretion started earlier and continued over a longer time period, and further that the amount of saliva secreted expressed per gland weight in response to submaximal doses of the sialogogue drug was bigger when compared with the rats on the pelleted bulk diet. These findings are interpreted as signs of a higher degree of sensitivity of the glands in the rats on the liquid diet than of those in the rats on the pelleted bulk diet.