Sweat gland function in isolated perfused skin.

Abstract

SUMMARY1. A technique for perfusion of skin has been used to investigate a possible neurochemical basis for the different patterns of sweating in domestic animals. Evaporative water loss was measured from excised trunk skin, ears or tails perfused with a nutrient Krebs solution, to which drugs were added as required. Perfused skin was observed to sweat in response to administration of sudorific drugs, and some features of the patterns of sweating were similar to those which could be induced by heating or by drugs in conscious animals.2. In sheep and goat skin, injections of adrenaline, and to a lesser extent of noradrenaline, elicited brief sweat discharges but these were not sustained when the drugs were infused during 10-20 min. Injections of isoprenaline, carbachol, 5-HT, bradykinin, oxytocin and histamine were all ineffective.3. Injections of adrenaline into cattle skin evoked longer-lasting sweat discharges, and infusions of adrenaline elicited continuous discharges. Injections of noradrenaline and sometimes of bradykinin caused only brief sweat discharges; other drugs were ineffective.4. In horse and donkey skin, injections or infusions of noradrenaline, oxytocin and bradykinin elicited brief discharges of sweat. Infusions of isoprenaline caused a continuous and profuse outflow of sweat. Infusions of adrenaline also caused a continuous discharge which was usually biphasic in its onset. Other drugs were ineffective.5. Assuming that the brief sweat discharges are due to myoepithelial contractions and the continuous discharges to sustained increases in secretion, equine sweat glands seem to have an ac-adrenergically controlled myoepithelium and a fi-adrenergically controlled secretary mechanism.Sheep and goats may have a similar ac-adrenergic control of the sweat gland * Present address:

Equine sweating and anhidrosis Part 1 – equine sweating

“…This is probably true also of oxytocin and Pitressin. Oxytocin and Pitressin administered intradermally had no stimulatory effect in vivo , 30 although brief discharges of sweat were elicited by large single injections of oxytocin in isolated perfused horse skin 70 . The presence of receptors for aldosterone is also doubtful.…”

“…A sweating response to intravenous histamine is apparently mediated via adrenaline release from the adrenal medulla 30,115 . 5‐HT when administered intradermally to horses caused no response and was ineffective on isolated perfused horse skin 70 . Even with an intravenous dose of 15 mg it was not clear that sweating resulted 30 .…”

“…This transient discharge following α‐adrenergic stimulation as opposed to the sustained output of greater magnitude and slower onset after β adrenergic stimulation, was assumed to be due to myoepithelial contraction. This led to the conclusion of an α adrenergically controlled myoepithelium and a β adrenergically controlled secretory mechanism 49,70 . Butorphanol (an α 2 agonist) induced sweating to some degree (usually around the poll and proximal third of the neck) in nine of 25 horses 173 .…”

“…During studies of isolated perfused horse skin, the glands were relatively insensitive to NA during perfusions that lasted many hours 70 . While Ad induced large and sometimes clearly biphasic discharges of sweat and isoprenaline (a β‐adrenoceptor agonist) induced large sweat discharges, which began 2–3 min after administration of the drug and were maintained, NA induced rapid but only small discharges of sweat.…”

“…Adrenaline has a direct action on the equine sweat gland. The glands in isolated perfused horse skin remain very sensitive to it and to the adrenoceptor agonist isoprenaline during perfusions that last many hours 70 . Single equine glands can secrete for more than an hour in response to adrenaline 5 .…”