1 Previous studies have shown that ATP and UTP are able to stimulate phospholipase C (PLC) and proliferation in cultured aortic smooth muscle cells. Here we set out to characterize the receptor responsible, and investigate a possible role for p42 and p44 mitogen activated protein kinase (MAPK) in the proliferative response. 2 The phospholipase C response of spontaneously hypertensive rat (SHR) derived aortic smooth muscle cells in culture showed that the response to ATP was partial compared to the response to UTP. 3 Further studies characterized the responses of the SHR derived cells. UTP was the only full agonist with the SHR cells; UDP gave a partial response while ADP, 2-methythio-ATP and a,b-methylene ATP were essentially ineective. The response to UDP was almost lost in the presence of hexokinase, consistent with this being due to extracellular conversion to UTP. These observations are inconsistent with the response being mediated by either P2Y 1 or P2Y 6 receptors. 4 When increasing concentrations of ATP were present with a maximally eective concentration of UTP, the size of the response diminished, consistent with UTP and ATP acting at a single population of receptors for which ATP was a partial agonist. This is inconsistent with a response mainly at P2Y 2 receptors. 5 1321N1 cells transfected with human P2Y 4 receptors gave a similar agonist response pro®le, with ATP being partial compared to UTP, loss of response to UDP with hexokinase treatment, and with the response to UTP diminishing in the presence of increasing concentrations of ATP. 6 Use of the reverse transcriptase-polymerase chain reaction con®rmed the presence of mRNA encoding P2Y 4 receptors in SHR derived vascular smooth muscle cells. Transcripts for P2Y 2 , P2Y 4 and P2Y 6 receptors, but not P2Y 1 receptors, were detected. 7 Stimulation of SHR derived cells with UTP enhanced the tyrosine phosphorylation of both p42 and p44 MAPK, and the incorporation of [ 3 H]-thymidine into DNA. Both these responses were diminished in the presence of an inhibitor of activation of MAPK. 8 These results lead to the conclusion that in SHR derived cultured aortic smooth muscle cells, PLC responses to extracellular UTP and ATP are predominantly at P2Y 4 receptors, and suggest that these receptors are coupled to mitogenesis via p42/p44 MAPK.

Donation after Cardiac Death (DCD)is an increasingly important source of kidney transplants, but because of concerns of ischemic injury during the agonal phase, many centers abandon donation if cardiorespiratory arrest has not occurred within 1 h of controlled withdrawal of life-supporting treatment (WLST). We report the impact on donor numbers and transplant function using instead a minimum 'cut-off' time of 4 h. The agonal phase of 173 potential DCD donors was characterized according to the presence or absence of: acidemia; lactic acidosis; prolonged (>30 min) hypotension, hypoxia or oliguria, and the impact of these characteristics on 3-and 12-month transplant outcome evaluated by multivariable regression analysis. Of the 117 referrals who became donors, 27 (23.1%) arrested more than 1 h after WLST. Longer agonal-phase times were associated with greater donor instability, but surprisingly neither agonal-phase instability nor its duration influenced transplant outcome. In contrast, 3-and 12-month eGFR in the 190 transplanted kidneys was influenced independently by donor age, and 3-month eGFR by cold ischemic time. DCD kidney numbers are increased by 30%, without compromising transplant outcome, by lengthening the minimum waiting time after WLST from 1 to 4 h.

It is essential to minimize the unnecessary discard of procured deceased donor kidneys, but information on discard rates and the extent to which discard can be avoided are limited. Analysis of the UK Transplant Registry revealed that the discard rate of procured deceased donor kidneys has increased from 5% in 2002-3 to 12% in 2011-12. A national offering system for hard-to-place kidneys was introduced in the UK in 2006 (the Declined Kidney Scheme), but just 13% of kidneys that were subsequently discarded until 2012 were offered through the scheme. In order to examine the appropriateness of discard, 20 consecutive discarded kidneys from 13 deceased donors were assessed to determine if surgeons agreed with the decision that they were not implantable. Donors had a median (range) age of 67 (31-80) yr. Kidneys had been offered to a median of 3 (1-12) centers before discard. Four (20%) of the discarded kidneys were thought to be usable, and nine (45%) were possibly usable. As a result of these findings, major changes to the UK deceased donor kidney offering system have been implemented, including simultaneous offering and broader entry criteria for hard-to-place kidneys. Organizational changes are necessary to improve utilization of deceased donor kidneys.

LDN removes some of the disincentives to live donation without compromising the outcome of the recipient transplant.