Relations of prolactin and thyroid hormone to molting, skin texture, and cutaneous secretion in the red‐spotted newt

Abstract

The effects of prolactin on skin texture, on cutaneous secretion and on molting have been examined in the red-spotted newt under several hormonal conditions. In the adult newt skin is smooth and is covered with varying amounts of cutaneous secretion. Under laboratory conditions the skin ordinarily becomes rough and tuberculated within one or two weeks. Doses of 1.2-120 units of prolactin caused the skin of intact, laboratory-conditioned, red-spotted newts to become smooth and slimy. Similar changes were seen in newts bearing pituitary autografts which are presumed to secrete excessive amounts of prolactin or prolactin-like hormone. No change in skin texture or secretion was detected in hypophysectomized newts treated with prolactin. It has been reported recently that 120 units of prolactin induces molting in the hypophysectomized European crested newt (Vellano et al., '70). Although 3 of 15 hypophysectomized red-spotted newts molted in response to that dose of prolactin, TSH in amounts equivalent to that which may have contaminated the prolactin produced similar results. Thyroidectomized newts showed no cutaneous response to 120 units of prolactin. Thyroidectomized newts kept i n water to which 10 pgm/liter of 1-thyroxine had been added molted only rarely, but when thyroidectomized animals were put into 10 pgm/liter of 1-thyroxine and injected with 12 units of prolactin they began to molt normally and their skins became smooth and slimy. It is concluded that in the red-spotted newt prolactin alone does not induce molting but may facilitate molting, probably through the stimulation of cutaneous secretion, when introduced with thyroid hormone. It is further concluded that although prolactin induces changes in skin texture and in cutaneous secretion, those responses are to some extent mediated by the thyroid hormone.It has long been accepted that the thyroid is the endocrine gland that exercises primary control over molting in the urodeles (Adams and Richards, '29; Adams, Kuder and Richards, '32; Osborn, '36; Jmrgensen and Larsen, '60; Clark and Kaltenbach, '61). Recently, however, it has been reported that prolactin induces molting in hypophysectomized (Vellano et al., '70) and in thyroidectomized and castrated (Vellano, Mazzi and Sacerdote, '70) specimens of the European crested newt (Triturus cristatus carnifex). Although rejected by some workers (Adolph and Collins, '25; Adams and Gierson, '32; Clark and Kaltenbach, '61), the suggestion has been put forth (Schultz, 1889; Dennert, '24; Chadwick, '48), that in J. EXP. ZOOL, 184 36S382 molting, cutaneous secretion accumulates beneath the slough, forcing it from the body. Various findings have given indication that prolactin affects skin texture and cutaneous secretion both in the redspotted newt (Adams, '32; Reinke and Chadwick, '40; Grant and Grant, '58) and in the crested newt (Vellano, Mazzi and Sacerdote, '70).The present study explores the question of whether or not prolactin is capable of stimulating molting in the red-spotted newt (Notophthalmus v...

Calcineurin/Nfatc1 signaling links skin stem cell quiescence to hormonal signaling during pregnancy and lactation

“…Prl can control skin molting in newts (Dent et al 1973) and feather molting in avian species (Dawson and Sharp 1998;Dawson et al 2009;Crossin et al 2012). Seasonal Prl in combination with other hormones is thought to modulate annual changes in hair growth of several species, including sheep, deer, and voles (Duncan and Goldman 1984;Curlewis et al 1988;Smale et al 1990;Dicks et al 1996;Nixon et al 2002;Randall 2007).…”

Prolactin alters the expression of integumental glycoconjugates in the red‐spotted newt, Notophthalmus viridescens

“…The second metamorphosis includes PRL-induced changes in which the rough skin of the eft becomes smooth and slimy. Similar changes can be induced in the adult (Dent et al, 1973;Dent, 1975). In adult newts, prolactin functions singly, or in combination with testosterone, to promote the development of male secondary sexual characteristics including increased tail fin height (Chadwick, 1940, 19411, formation of nuptial pads (Singhas and Dent, 1975) and stimulation of product synthesis and discharge from hedonic glands (Pool and Dent, 1977).…”

“…that when newts of either sex are maintained in water at 4"C, skin texture and cutaneous secretory activity remain constant; however, when animals are maintained at 22-23"C7 the epidermis becomes rough and secretory activity diminishes within 2-3 weeks (Dent et al, 1973;Hoffman and Dent, 1978). Similarly, it has been observed that during the summer months the skin of freshly collected animals lacks the smooth and slimy texture that persists during the remainder of the year (Singhas, unpublished).…”

Prolactin: Fishy Tales of Its Primary Regulator and Function

“…In reptiles and amphibians, PRL promotes molting of the epidermis. 17 PRL stimulates skin melanocyte growth in fishes and mammals, 18,19 and keratinocyte growth in mammals. 20 In birds, PRL induces defeathering and epidermal growth of the incubation patch.…”