1 This study has investigated the eects adenosine 5'-triphosphate (ATP), analogues of ATP, uridine 5'-triphosphate (UTP) and adenosine on prostaglandin output from the guinea-pig uterus superfused in vitro, and from guinea-pig endometrium and myometrium cultured for 24 h. 2 ATP, 2-methylthio ATP and adenosine increased the outputs of prostaglandin F 2a (PGF 2a ) and 6-keto-PGF 1a (re¯ecting PGI 2 production), and UTP increased the output of PGF 2a from the superfused guinea-pig uterus. These ®ndings support the hypothesis that the contractile eects of ATP, 2-methylthio ATP, UTP and adenosine are mediated by prostaglandins. 3 Suramin (a P2 receptor antagonist) and 8-sulphophenyltheophylline (an A receptor antagonist) blocked the stimulatory actions of ATP and adenosine, respectively, on PGF 2a output, suggesting that ATP acts on P2 receptors (probably of the P2Y type) and adenosine acts on A receptors in the guinea-pig uterus to increase PGF 2a production. 4 ATP, 2-methylthio ATP, a,b-methylene ATP, b,g-methylene ATP, UTP and adenosine increased the output of PGF 2a from guinea-pig endometrium and myometrium after 24 h of culture, with a greater stimulatory eect being exerted on the endometrium than on the myometrium. Little or no stimulatory eect was seen after 2 and 8 h of culture. In addition the eects of ATP, ATP analogues, UTP and adenosine on the outputs of PGE 2 and 6-keto-PGF 1a from cultured endometrium and myometrium were more variable, with both stimulation and inhibition being observed. 5 The stimulatory eects of ATP and adenosine on PGF 2a output from the endometrium and myometrium were associated with an increase in the prostaglandin synthesizing capacity of both tissues, due probably to an increase in the amount of prostaglandin H synthase present.
A cytological study was made of the anterior submaxillary gland of the domestic chicken a t 1 day, 4 days, and 10 months of age. This gland is one of a number of aggregates distributed throughout the mouth and along the oesophagus. I t is a compound tubular gland, whose ducts open in several places under the tongue. T h e glandular epithelium is a single layer of tall prismatic inucous cells. There are no serous cells. Most of the cells are loaded with mucus and the nuclei are flattened a t the bases of the cells. T h e cells present various stages of secretory activity. No mitotic figures were seen. Tests for alltaline phosphatase were negative, but there was strong acid phospl~atase activity. Lipase activity was slight but present. The Golgi material is composed of rods and granules lying between the nucleus and the lumen of the gland.
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