The Role of Prolactin in Thermoregulation and Water Balance During Heat Stress in Domestic Ruminants

Prolactin is a multi functional hormone that is believed to possess various diverse biological potencies than all other pituitary hormones combined. It is widely understood that prolactin is positively associated with ambient temperature that may indicate involvement of prolactin in an acclimatory responses to higher ambient temperature. The current review presented the evidences that indicate the possible modulatory role of prolactin in some thermoregulatory mechanisms during hot climates in domestic ruminants. The observed thermoregulatory failure with the suppression of prolactin response to heat exposure in ruminants suggests the modulation of prolactin of some thermoregulatory mechanisms. Down regulation in the expression of genes associated with prolactin signaling pathways in some target tissues which is induced by thermal exposure may be consistent with mechanisms to down-regulate some metabolic process directed to reduce heat increment. Evidence suggests that prolactin may affect body fluid regulation by maintaining extracelluar fluid volume during heat exposure and hence supporting heat dissipation. Prolactin may also control seasonal pelage growth cycle probably directed to facilitate heat loss during summer season. It can be concluded that higher circulating prolactin may modulate some thermoregulatory processes during heat exposure. This is likely to be associated with modulation of some mechanisms of heat dissipation and heat production oriented to support homeothemy.