Sardine procalcitonin amino-terminal cleavage peptide has a different action from calcitonin and promotes osteoblastic activity in the scales of goldfish.

The nucleotide sequence of a sardine preprocalcitonin precursor has been determined from their ultimobranchial glands in the present study. From our analysis of this sequence, we found that sardine procalcitonin was composed of procalcitonin amino-terminal cleavage peptide (N-proCT) (53 amino acids), CT (32 amino acids), and procalcitonin carboxyl-terminal cleavage peptide (C-proCT) (18 amino acids). As compared with C-proCT, N-proCT has been highly conserved among teleosts, reptiles, and birds, which suggests that N-proCT has some bioactivities. Therefore, both sardine N-proCT and sardine CT were synthesized, and their bioactivities for osteoblasts and osteoclasts were examined using our assay system with goldfish scales that consisted of osteoblasts and osteoclasts. As a result, sardine N-proCT (10-7M) activated osteoblastic marker enzyme activity, while sardine CT did not change. On the other hand, sardine CT (10-9 to 10-7M) suppressed osteoclastic marker enzyme activity, although sardine N-proCT did not influence enzyme activity. Furthermore, the mRNA expressions of osteoblastic markers such as type 1 collagen and osteocalcin were also promoted by sardine N-proCT (10-7M) treatment; however, sardine CT did not influence their expressions. The osteoblastic effects of N-proCT lack agreement. In the present study, we can evaluate exactly the action for osteoblasts because our scale assay system is very sensitive and it is a co-culture system for osteoblasts and osteoclasts with calcified bone matrix. Both CT and N-proCT seem to influence osteoblasts and osteoclasts and promote bone formation by different actions in teleosts.

Potencies of centrally- or peripherally-injected full-length kisspeptin or its C-terminal decapeptide on LH release in intact male rats.

The aim of the present study was to compare the effects of full-length rat kisspeptin (rKp-52) with C-terminal decapeptide (Kp-10) of rat or human kisspeptin on LH release in intact male rats. Plasma LH profiles were determined by frequent blood sampling at 6-min intervals for 3 h after central or peripheral injection of kisspeptins. Intracerebroventricular (icv) injection of rKp-52 (0.1 nmol) induced a gradual increase in the plasma LH level, which remained high for the rest of the sampling period. On the other hand, icv injection of rKp-10 did not increase the plasma LH level at the same dose (0.1 nmol). A 10-times higher dose (1 nmol) of rKp-10 and hKp-10 increased the plasma LH level, but the increase was lower than that of rKp-52 icv injection. Intravenous (iv) injection of kisspeptins also stimulated LH release at 10 or 100 nmol/kg. In rKp-52 (10 nmol/kg)-treated animals, the plasma LH level reached a peak within 30 min and remained high until 60 min postinjection. The rKp-10- and hKp-10-injected animals showed a more rapid decline in plasma LH level after the peak found at around 30 min after the injections at both middle (10 nmol/kg) and high (100 nmol/kg) doses. The present study indicates that full-length kisspeptin is more effective in stimulating LH release compared with Kp-10 in male rats. The difference in LH-releasing activity may be the result of a difference in degradation of the peptides, but it is still worth determining whether an active domain other than the C-terminal decapeptide is present in full-length kisspeptin.

Identification of angiotensin I in a cyclostome, Lampetra fluviatilis.

Angiotensin I (ANG I) was isolated from incubates of plasma and kidney extracts of the river lamprey, Lampetra fluviatilis, using eel vasopressor activity as an assay during purification. Its sequence was Asn-Arg-Val-Tyr-Val-His-Pro-Phe-Thr-Leu as determined by the sequence analysis and mass spectrometry. The sequence was confirmed by identity of the elution profile with the synthetic peptide in two different reverse-phase columns of high-performance liquid chromatography. Lamprey ANG I produced dorsal-aortic pressor responses in L. fluviatilis but the rise was very small in comparison to that produced by angiotensin II. Angiotensin III produced an even bigger increase. It was not possible to demonstrate a difference in response to Asn(1) (lamprey) ANG I and Asp(1) (human) ANG I. The present study directly demonstrated the presence and biological activity of the renin-angiotensin system in the most primitive extant vertebrates, the cyclostomes. Thus the renin-angiotensin system is a phylogenetically old hormonal system that is present throughout the vertebrates.