Sexton, who will start at fly-half against Wales on Saturday, informed the Irish Rugby Football Union that he would be leaving Leinster at the end of the season, with Racing Metro his expected destination.
Leinster colleague Rob Kearney revealed that Sexton was "upset" by the way negotiations unfolded and did not want to leave Dublin.
It has been reported that Sexton was disappointed not to have been offered parity with Heaslip, but Ireland's new captain denied the issue had affected their relationship.
When asked if there was any tension between himself and Sexton, Heaslip replied: "No, not in the slightest.
"It (France) has always been there, it's not like it's a new ball park. I doubt Jonny's thinking about being a guinea pig for anyone else.
"There hasn't been much chat except a bit of banter and trying to speak French to him.
"Jonny had to weigh up the offers and chose the option he chose. As a club-mate at Leinster and friend it's disappointing to lose him. We're going to miss him.
"It will be an amazing adventure for him and I'm sure he's looking forward to it.
"He's the ultimate professional. He came in on Sunday night and was good to go.....as cranky as ever. The business is done and now he's onto the next challenge."
Ireland have restored centre Brian O'Driscoll, full-back Kearney, hooker Rory Best and openside Sean O'Brien to their starting XV against Wales after the influential quartet missed the autumn through injury.
The exciting Craig Gilroy and Simon Zebo have been named on the wings as Ireland seek to end their three-match losing streak against the Grand Slam champions at the Millennium Stadium on Saturday.
"Wales are the champions, we're going to their back yard and they'll be smarting from their disappointing November, so we know we're fully up against it," coach Declan Kidney said.
"The Six Nations has now become unique in that there is no back door - there are no bonus points or home and away games like there are in the Heineken Cup.
"It's not quite knock-out rugby but if you get off to a good start in your first game, it gives you a great chance to go on and do things."
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