The effect of Na⁺ depletion on the Na⁺:K⁺ ratio of the parotid saliva of the sheep

Abstract

It is well known that the continued removal of gastric juice from animals or man does not radically alter the composition of the juice (Dragstedt & Ellis, 1930; Katsch & Mellinghoff, 1933). This was found despite the loss of up to half the body chlorides (Lim & Ni, 1925-6). McCance (1938) reviewed the literature on the effect of salt deficiency on the electrolyte composition of body secretions. In his own experiments he produced depletion by a deficient diet and repeated sweats. The depletion was great enough to reduce the extracellular chlorides of his subjects by 40-50 %.He found that in mixed saliva, gastric secretion and sweat there was a fall in Na+ concentration and a rise in K+ concentration. However, the changes in the first two were small, i.e. roughly reciprocal changes in Na+ and K+ of about 5-10 m-equiv/l. In the case of sweat glands, the Na+ and C1-loss in each episode decreased with increasing depletion. Whereas initially 150-180 m-equiv Na+ were lost each time, finally (7th-8th day) only 60-80 m-equiv were lost in about the same volume. There was a small gradual rise (5-10 m-equiv) in the K+ loss.Gross Na+ depletion has been produced in dogs by pancreatic fistulae (Gamble & McIver, 1928;Hartmann & Elman, 1929;Johnston & Ball, 1930).The total base concentration of the pancreatic secretion decreased as the total base of the plasma decreased. The observations of Johnston & Ball (1930), though not conclusive on this point, indicate that there was no rise of K+ in the pancreatic juice as the animal became Na+ depleted. This paper is concerned with reporting a rather striking relation between the electrolyte balance of the sheep and the composition of parotid gland secretion.The normal sheep secretes 4-8 1. of alkaline parotid saliva each day. This buffers the products of bacterial fermentation in the rumen. The transplantation of one parotid papilla and duct on to the cheek permits the subtraction of

The rate of flow and composition of various salivary secretions in sheep and calves

“…Denton (1957 a) showed that parotid secretion was wholly inhibited in untrained sheep when they were forcibly laid on their sides. Denton (1956) and of Coats & Wright (1957). Denton (1957b) found that the total electrolyte concentration of parotid saliva was considerably greater than that of plasma and thus regarded the saliva as being hypertonic to plasma.…”

“…The samples were collected under conditions of alternating rest and reflex stimulation of the parotid from the oesophagus and reticulorumen, but no stimuli were applied to the mouth. Denton (1956) and of Coats & Wright (1957). For example, parotid saliva was collected continuously for 8 days from an adult sheep, Sheep 5, that had been trained to drink saliva from a bottle.…”

“…Sheep parotid saliva consists of a solution of sodium, potassium, bicarbonate, phosphate and a little chloride (McDougall, 1948), and the relative proportions of these salts are affected by the rate of secretion (Coats & Wright, 1957) and by sodium depletion (Denton, 1956). Relatively little is known of the composition of submaxillary and sublingual saliva or of the secretions of the small glands of the mouth.…”

Sodium depletion of pregnant ewes and its effects on foetuses and foetal fluids

“…No supplementary salt was allowed during sodium depletion, but water was allowed ad libitum. Sodium depletion was induced by draining saliva from the right parotid gland (Denton, 1956;Dobson, Kay & McDonald, 1960). Data on maternal parameters were collected from both the depletion and the control ewes on the day of commencement of sodium depletion and on the day before Caesarean section.…”

Salivary Electrolyte Concentrations and Electrical Potential Difference Across the Parotid Salivary Duct of Anaesthetized Sodium-Replete Sheep

“…(6) In rat and human parotid ,glands and cat submandibular glands, similar salivary electrolyte patterns have been observed after both parasympathomimetic stimulation and parasympathetic nerve or reflex stimulation of flow (Hildes and Ferguson 1955;Schneyer and Hall 1965;Mangos and Braun 1966;Petersen and Poulsen 1967;Knauf and Fr6mter 1970a;Kaladelfos and Young 1974). In sodium-deficient sheep, mineralocorticoids acton the duct system of the parotid gland causing increased reabsorption of sodium in exchange for potassium (Blair-West et al 1969;Compton and Young 1976) and under these conditions concentration of sodium in the saliva should be ap.d is positively correlated with salivary flow (Denton 1956;Beal et al 1975). For salivary sodium concentration to be negatively correlated with flow this mineralocorticoid-dependent reabsorption of sodium must be minimal and thus the Na + /K + concentration ratio of the saliva should be high.…”