140
A. M. PERKS
peptides have strong influences on salt metabolism, but 8 Lys vasopressin
is ineffective (Maetz, 1963).
Clearly, milk-ejection activity is meaningless in an elasmobranch. An
oxytocic action would be more understandable, but no author has reported stimulation of the gravid or nongravid elasmobranch oviduct by
either mammalian or elasmobranch extracts. Dreyer (1946) applied an
ox pituitary extract (10 mU/ml, perfusing medium) to the isolated oviduct of Raia erinuca, Squulus acanthias, Mustelus canis and Prwnace
ghuca and failed to obtain a response. He found that extracts from
Squalus acanthh were equally ineffective. Similarly, Perks (1959; Dodd
et al., 1966) found that oxytocin in doses up to 40 mU/ml, or an extract
equivalent to one-half of a neurointermediate lobe of Squalus acanthias
per 62 ml of bathing medium, had no effect on the isolated oviduct of
mature Scylwrhinus canieulus nor on uterine strips from near-term, pregnant Squulus acanthius. Effects on other smooth muscles are not as consistently negative. Dreyer (1946) failed to find effects of pituitary extracts
on the stomach or intestinal muscle of the same species as those in which
he tested the oviducts. However, M. E. Sawyer (1933) utilized high doses
of whole ox pituitary extract (5000 mu, injected intravenously, intact
preparation; 25 mU/ ml supporting medium, isolated preparation ) and
observed rhythmic contractions of mesenteric muscle of dogfish and skate
(Squalus acanthias, Raia sp.?) . Movements of the pyloric stomach were
also observed.
Despite the inconclusive effects of neurohypophysial principles on
smooth muscle, it appears that the peptides may be capable of producing
a vasopressor effect in the elasmobranchs. A marked and prolonged rise
of blood pressure, with inhibition of heart contractions, was found after
the injection of 5000 mu, whole mammalian pituitary extract (0.5 ml of
Burroughs Wellcome obstetrical Pituitrin) into Raia erinucea, R. diaphanes, R. scabrata, or R. stabuliforis) ( MacKay, 1931). A similar rise of
blood pressure occurred in the ventral aorta of Squalus acanthh after
the injection of various mammalian preparations (Halsey and Evans,
1937). In contrast, Waring et nl. (1950) found that arginine-lysine vasopressin had little effect on the elasmobranch blood pressure, although
there was a rise in the frequency and amplitude of the heartbeat, This
apparent disagreement could be explained if the vasopressor effects
within the elasmobranch circulation were vested in the oxytocin present
in the mammalian preparations (Dodd et al., 1966). If this were so, the
oxytocinlike principles which predominate in the elasmobranch pituitary
might be important pressor agents within their own species. Direct
experiments are needed in this field.
Since attempts to determine the systemic effects of neurohypophysial
A. M. PERKS
peptides have strong influences on salt metabolism, but 8 Lys vasopressin
is ineffective (Maetz, 1963).
Clearly, milk-ejection activity is meaningless in an elasmobranch. An
oxytocic action would be more understandable, but no author has reported stimulation of the gravid or nongravid elasmobranch oviduct by
either mammalian or elasmobranch extracts. Dreyer (1946) applied an
ox pituitary extract (10 mU/ml, perfusing medium) to the isolated oviduct of Raia erinuca, Squulus acanthias, Mustelus canis and Prwnace
ghuca and failed to obtain a response. He found that extracts from
Squalus acanthh were equally ineffective. Similarly, Perks (1959; Dodd
et al., 1966) found that oxytocin in doses up to 40 mU/ml, or an extract
equivalent to one-half of a neurointermediate lobe of Squalus acanthias
per 62 ml of bathing medium, had no effect on the isolated oviduct of
mature Scylwrhinus canieulus nor on uterine strips from near-term, pregnant Squulus acanthius. Effects on other smooth muscles are not as consistently negative. Dreyer (1946) failed to find effects of pituitary extracts
on the stomach or intestinal muscle of the same species as those in which
he tested the oviducts. However, M. E. Sawyer (1933) utilized high doses
of whole ox pituitary extract (5000 mu, injected intravenously, intact
preparation; 25 mU/ ml supporting medium, isolated preparation ) and
observed rhythmic contractions of mesenteric muscle of dogfish and skate
(Squalus acanthias, Raia sp.?) . Movements of the pyloric stomach were
also observed.
Despite the inconclusive effects of neurohypophysial principles on
smooth muscle, it appears that the peptides may be capable of producing
a vasopressor effect in the elasmobranchs. A marked and prolonged rise
of blood pressure, with inhibition of heart contractions, was found after
the injection of 5000 mu, whole mammalian pituitary extract (0.5 ml of
Burroughs Wellcome obstetrical Pituitrin) into Raia erinucea, R. diaphanes, R. scabrata, or R. stabuliforis) ( MacKay, 1931). A similar rise of
blood pressure occurred in the ventral aorta of Squalus acanthh after
the injection of various mammalian preparations (Halsey and Evans,
1937). In contrast, Waring et nl. (1950) found that arginine-lysine vasopressin had little effect on the elasmobranch blood pressure, although
there was a rise in the frequency and amplitude of the heartbeat, This
apparent disagreement could be explained if the vasopressor effects
within the elasmobranch circulation were vested in the oxytocin present
in the mammalian preparations (Dodd et al., 1966). If this were so, the
oxytocinlike principles which predominate in the elasmobranch pituitary
might be important pressor agents within their own species. Direct
experiments are needed in this field.
Since attempts to determine the systemic effects of neurohypophysial