Mitogenic effects of Brazilian arthropod venom on isolated islet beta cells: in vitro morphologic ultrastructural and functional studies.
BACKGROUND
One of the major pitfalls associated with use of isolated adult islets of Langerhans' cells is their minimal mitotic capacity. Consequently, maintenance of a steady viable islet cell mass is very difficult. To explore how to enhance beta-cell mitogenesis, we have examined the effects of venom fractions extracted from a Brazilian scorpion on morphologic and functional beta-cell patterns. The venom was previously known to induce nesidioblastosis-like effects with chronic hypoglycemia and pancreatitis in animal models.


METHODS
Venom fractions purified from Tityus bahiensis were incubated with batches of isolated rat islets, while a morphologic examination, glucose-stimulated insulin release, insulin content, and insulin messenger ribonucleic acid (mRNA) were carried out early during incubation. On fixation and double fluorescence immunolabeling (rhodamine for anti-insulin monoclonal antibodies; fluorescein for anti-5-bromodeoxyuridine), the preparations were imaged by confocal laser microscopy (CLM) for morphometric quantification of the mitoses. Insulin recovery and mRNA were also assessed at 21 days of culture.


RESULTS
Under CLM examination, the beta-cell mitotic rate significantly rose from 1 to 12.8% for the venom-exposed islets. At day 7, insulin release and content were significantly lower for the venom-exposed than the control islets. However, at day 21 of culture, insulin release in response to static incubation with glucose and insulin mRNA from the venom-exposed islets was higher than controls (p < .05).


CONCLUSIONS
Incubation with the scorpion venom induced a rapid and significant increase in the beta-cell proliferation not associated with a short-term increase in insulin secretion. The latter fully resumed and overcame controls later in culture, possibly after completion of the beta-cell expansion process.
Luca
Giovanni
G
Department of Internal Medicine, University of Perugia, Italy.
Calvitti
Mario
M
Basta
Giuseppe
G
Baroni
Tiziano
T
Neri
Luca M
LM
Becchetti
Ennio
E
Capitani
Silvano
S
Novaes
Geovana
G
Correa-Giannella
Maria Lucia
ML
Kalapothakis
Evanguedes
E
Engler
Sylva Stuchi Maria
SS
Eliaschewitz
Freddy Goldberg
FG
Sogayar
Mari Cleide
MC
Fanelli
Carmine
C
Brunetti
Paolo
P
Calafiore
Riccardo
R
D000818:Animals; D001973:Bromodeoxyuridine / Q000378:metabolism; D002452:Cell Count; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D007328:Insulin / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D008297:Male; D018613:Microscopy, Confocal; D008934:Mitogens / Q000737:chemistry / Q000633:toxicity*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012604:Scorpion Venoms / Q000737:chemistry / Q000633:toxicity*; D012605:Scorpions / Q000502:physiology*
D007328:Insulin; D008934:Mitogens; D012333:RNA, Messenger; D012604:Scorpion Venoms; D001973:Bromodeoxyuridine