Editor's report to authors

The manuscript by **** and colleagues desribes interesting studies on the purinoceptor on the rat megakaryocyie. In principle the study warrants publication but the manuscript cannot be accepted in its current form. The authors must provide adequate responses to the referee's criticisms and they should also deal with the following issues.

On pages 6 and 7, IC50 and EC50 estimates are quoted without standard errors. These should be given.

On page 6, regarding suramin, and on page 7, regarding RB-2, it is not valid to conclude that the antagonists are acting competitively. In order to confirm competitive action it would be necessary to perform full Schild analysis, involving the construction of complete ATP concentration response curves at a number of concentrations of antagonist. Since the authors haven't carried out such analysis the word 'competitive' should not be used. Similarly, on page 8, there is no evidence presented that ADP antagonism by suramin and RB-2 are competitive.

On page 10, Iine 9, how was the calculation made that the free forms of ATP and ADP are 1/30 of the total concentration?

In addition, the authors are requested to make the typographical changes and alterations to expression marked in red in the text.

Referee's report to authors

Manuscript 93 ***

I do not believe that this manuscript can be accepted in its present form. Acceptance would be conditional on either a moderation of the conclusions made or on provision of additional data to support the current conclusions. Specific points in support of this recommendation are made below:-

1) To my knowledge, Iiterature evidence for P2Y-selectivity of RB-2 is confined to　tissues with a mixed P2Y/P2x population. Critical to interpretation of data presented in this paper is whether RB-2 has an effect at P2T-Purinoceptors. Have the authors checked the activity of RB-2 at the P2T-subtype ? Without such evidence, the claim (pages 9 & 10) that the P2-purinoceptor on rat megakaryocytes represents a novel subtype is unsound. Inhibition of the megakaryocyte response to ADP and ATP by suramin is a novel finding but is insufficient evidence for a novel P2-subtype.

2) In the absence of the information discussed in (1), the strongest evidence that the purinoceptor on rat megakaryocyies differs from the platelet receptor is the observation that ATP functions as an agonist. However, the relative potencies of ADP and ATP (ADP 30x ATP) introduces some concern. A 3% contamination of the ATP source with ADP or a 3% breakdown of ATP to ADP under the conditions of the experiment would yield sufficient ADP to artifactually make ATP appear to be an agonist. Do the authors have purity and stability data for their ATP solutions ? This is an important point to address in order to be certain that the claim for a different receptor is not merely a reflection of an experimental artifact.

3) The last sentence of the Abstract is currently inconsistent with the main conclusion in the paper. The main thrust of the paper is currently that the P2-subtype on rat megakaryocytes is a new subtype. As written, I would conclude from point 4 of the Abstract that the authors are saying that the receptor is a P2-rather than P1-purinoceptor.

4) The first mention of the use of the Pl-antagonist, 7-chlorotheophylline is on page 7 in the results section. The rationale for the use of this agent, along with its source should appear in the methods section.

5) I think the authors may have mis-quoted their own work on pages 9 & 10 in the sentences beginning "As the agonist selectivity..." and "In our previous report...". In each case, "(**** et al, 1993a)" should, I think, read "(**** et al, 1993b)".

6) Minor suggested textual alterations and corrections of typographical errors throughout the manuscript have been noted in pencil.