Recovery of fertility after grafting of cryopreserved germinative tissue in female rabbits following radiotherapy.

BACKGROUND: Many cancer survivors face infertility as a consequence of the aggressive treatment they must undergo. Cryopreservation of ovarian tissue before chemotherapy or radiotherapy may allow for tissue transplantation after the treatment, and restoration of fertility. We tested the potential of an orthotopic autografting of cryopreserved germinative tissue in female rabbits with ovarian failure following radiotherapy. METHODS: Ten adult multiparous female rabbits were randomly allocated into two groups, five in group I (control) and five in group II (transplant). All rabbits underwent right oophorectomy with cryopreservation of the germinative tissue, followed by sterilization of the remaining left ovary by radiotherapy. Later, group II rabbits received in the irradiated left ovary an implant of the frozen germinative tissue from the right ovary, whose small pieces were freely spread intracortically in a procedure we named 'intracortical sowing of germinative tissue' (ISGT). RESULTS: All group II rabbits conceived following spontaneous mating within 6 months of the transplant, whereas none of the remaining rabbits in group I had conceived up to 11 months after transplant. CONCLUSIONS: This study suggests that fertility can be restored in rabbits by sowing cortical tissue in a previously irradiated ovary. The clinical feasibility of this technique remains to be determined.

Hepatic heterogeneity in the response to ATP studied in the bivascularly perfused rat liver.

The zonation of the purinergic action of ATP in the hepatic parenchyma was investigated in the bivascularly perfused rat liver by means of anterograde and retrograde perfusion. Livers from fed rats were used, and ATP was infused according to four different experimental protocols: (A) anterograde perfusion and ATP infusion via the portal vein; (B) anterograde perfusion and ATP via the hepatic artery; (C) retrograde perfusion and ATP via the hepatic vein; (D) retrograde perfusion and ATP via the hepatic artery. The following metabolic parameters were measured: glucose release, lactate production and oxygen consumption. The hemodynamic effects were evaluated by measuring the sinusoidal mean transit times by means of the indicator-dilution technique. ATP was infused during 20 min at four different rates (between 0.06-0.77 micromol min[-1] g liver[-1]; 20-200 microM) in each of the four experimental protocols. The results that were obtained allow several conclusions with respect to the localization of the effects of ATP along the hepatic acini: (1) In retrograde perfusion the sinusoidal mean transit times were approximately twice those observed in anterograde perfusion. ATP increased the sinusoidal mean transit times only in retrograde perfusion (protocols C and D). The effect was more pronounced with protocol D. These results allow the conclusion that the responsive vasoconstrictive elements are localized in a pre-sinusoidal region; (2) All hepatic cells, periportal as well as perivenous, were able to metabolize ATP, so that concentration gradients were generated with all experimental protocols. Extraction of ATP was more pronounced in retrograde perfusion, an observation that can be attributed, partly at least, to the longer sinusoidal transit times. In anterograde perfusion, the extraction of ATP was time-dependent, a phenomenon that cannot be satisfactorily explained with the available data; (3) ATP produced a transient initial inhibition of oxygen uptake when protocols A and B were employed. These protocols are the only ones in which the cells situated shortly after the intrasinusoidal confluence of the portal vein and the hepatic artery were effectively supplied with ATP. The decrease in oxygen consumption was more pronounced at low ATP infusions when protocol B was employed. These observations allow the conclusion that the former phenomenon is localized mainly in cells situated shortly after the intrasinusoidal confluence of the portal vein and hepatic artery. Oxygen consumption in all other cells, especially the proximal periportal ones, is increased by ATP; (4) In agreement with previous data found in the literature, glycogenolysis stimulation by ATP was more pronounced in the periportal region. The cells that respond more intensively are not the proximal periportal ones, but those situated in the region of the intrasinusoidal confluence of the portal vein and the hepatic artery.

Hepatic heterogeneity in the response to AMP studies in the bivascularly perfused rat liver.

The zonation of the purinergic action of AMP in the hepatic parenchyma was investigated in the bivascularly perfused rat liver by means of anterograde and retrograde perfusion. Livers from fed rats were used and AMP (100 microM) was infused according to four different experimental protocols: (A) anterograde perfusion and AMP infusion via the portal vein; (B) anterograde perfusion and AMP infusion via the hepatic artery; (C) retrograde perfusion and AMP via the hepatic vein; (D) retrograde perfusion and AMP via the hepatic artery. The response of the liver cells was heterogeneous. Oxygen uptake inhibition by AMP predominates in cells situated shortly after the intrasinusoidal confluence of the portal vein and hepatic artery. Oxygen consumption in all other cells seems to be increased by AMP. Glycogenolysis stimulation by AMP (glucose release) was more pronounced in the periportal cells situated in the region of the intrasinusoidal confluence of the portal vein and the hepatic artery. It can be concluded that the heterogenic response of the liver to AMP is similar to the heterogenic response to ATP.