2. THE NEUROHYPOPHYSIS
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Table I
The Structure of the Neurohypophysial Principles of Fish and other Vertebratesa
A. Basic Vasopressor Principles
1. Arginine vasotocin
I
I
Cys Tyr Ile
Gln
Asn
Cys Pro Arg Gly(NHt)
1
2
3
4
5
6
7
8
9
Exists in all fish; possibly in all vertebrates, a t some stage of development
2. Arginine vasopressin
I
Phe
CYS
Arg
I
I
CYS
Exists in most mammals, except the pig family
3. Lysine vasopressin
I
I
Phe
CYS
LYS
I
CYS
Exists in mammah of the pig family
B. Neutral Oxytocinlike Principles
4. Oxytocin
I
Ile
CYS
Leu
I
I
CYS
Exists in mammals, birds, reptiles, amphibia (?), Dipnoi (?), and holocephalians (?)
5. 8 Ile oxytocin (“Mesotocin”)
Ilc
CYS
Ile
I
I
I
CYS
Exists in reptiles, amphibia, and Dipnoi
6. 4 Ser, 8 Ile oxytocin (“icthyotocin,” “isotocin”)
cysIle . Ser
CYSIle
I
I
Exists in teleosts, holosteans, and brachiopterygians
7. 4 Ser, 8 Glu(NH2) oxytocin (“glumitocin”)
I
I
Ile . Ser
c y s d
l
n
CysI
Exists in elasmobranchs, particularly skate
8. Unknown elasmobranch oxytocic principle (EOPI) (Val, Ser peptide@)?).
Exists in Squalus ucanthias, and perhaps other sharks
_ _ _ _ _ ~
a Note: amino acids indicated by lines only are the same as those present in arginine
vasotocin.